On April 19, 1943, Swiss chemist Albert Hofmann rode his bicycle home from work through the streets of Basel. This would normally be an unremarkable event, but Hofmann had just deliberately ingested 250 micrograms of a substance he had synthesized five years earlier: lysergic acid diethylamide, or LSD. What followed was the world’s first intentional acid trip, and the bicycle ride became legendary in psychedelic culture as “Bicycle Day.”
The Background
Albert Hofmann worked for Sandoz Pharmaceuticals in Basel, Switzerland. He was researching derivatives of ergot, a fungus that grows on rye and other grains. Ergot contains various alkaloids with interesting pharmaceutical properties, though it’s also historically responsible for poisoning epidemics.
In 1938, Hofmann synthesized LSD-25 (the 25th compound in his ergot research series) as part of a program searching for useful medications. Initial tests on animals showed some circulatory and respiratory effects, but nothing remarkable. The compound was shelved, considered uninteresting.
Five years later, Hofmann had what he later described as a peculiar presentiment that LSD-25 might have properties worth investigating further. On April 16, 1943, he decided to synthesize a fresh batch.
The First Trip: An Accident
While working with LSD on April 16, Hofmann inadvertently absorbed a small amount through his skin. He began feeling strange: restless, dizzy, with slightly altered perception. He went home early.
At home, lying down, he experienced what he later described as “an uninterrupted stream of fantastic pictures, extraordinary shapes with intense, kaleidoscopic play of colors.” The effects lasted about two hours, then gradually faded.
Hofmann was intrigued. He suspected the LSD had caused these effects, but the amount absorbed must have been tiny. If such a small dose produced such profound effects, this was an extraordinarily potent substance—far more powerful than any known psychoactive compound.
The Intentional Experiment
Hofmann decided to conduct a self-experiment—a practice not uncommon among chemists of his era, though discouraged today. He needed to determine if LSD had indeed caused his experience and, if so, what dose was active.
Based on his knowledge of ergot alkaloids, he estimated an active dose would be around 0.25 milligrams (250 micrograms). This seemed conservative; it’s equivalent to a few grains of salt. Hofmann had no way to know that LSD is active at doses as low as 20-50 micrograms. His “conservative” dose was actually massive—roughly five times a typical recreational dose today.
On April 19, 1943, at 4:20 PM, Hofmann dissolved 250 micrograms of LSD in water and drank it. He noted the time in his lab journal and waited.
The Bicycle Ride
At 5:00 PM, Hofmann began feeling dizzy and anxious. His visual perception started to distort. Alarmed, he asked his laboratory assistant to escort him home. World War II was ongoing, and gasoline was rationed, so automobiles weren’t an option. They traveled by bicycle.
Hofmann later wrote: “On the way home, my condition began to assume threatening forms. Everything in my field of vision wavered and was distorted as if seen in a curved mirror. I also had the sensation of being unable to move from the spot. Nevertheless, my assistant later told me that we had traveled very rapidly.”
This disconnect between Hofmann’s subjective experience (feeling frozen in place) and objective reality (moving quickly) became a characteristic feature he would later identify in LSD experiences: the profound alteration of time perception and sensory processing.
The Peak Experience
Once home, Hofmann’s experience intensified dramatically. He feared he was losing his mind or dying. His body felt strange, his furniture seemed to move and breathe, and colors became overwhelmingly vivid. He called a doctor.
The doctor arrived, examined Hofmann, and found nothing physically wrong—normal blood pressure, normal pulse. But clearly something was happening. Hofmann was experiencing the full force of an LSD peak.
His notes from later, when he had recovered enough to write, describe: “A demon had invaded me, had taken possession of my body, mind and soul. I jumped up and screamed, trying to free myself from him, but then sank down again and lay helpless on the sofa.”
The furniture assumed “grotesque, threatening forms.” Time lost all meaning. Hofmann felt as though he were outside his body, watching himself from a distance.
The Neighbor
Hofmann’s neighbor, a woman who brought milk, appeared in his hallucinations as a “malevolent, insidious witch.” This terrified him. In reality, she was simply delivering milk, concerned about the doctor’s presence. But to Hofmann, lost in LSD’s reality-altering effects, she seemed demonic.
This experience highlighted LSD’s ability to transform mundane stimuli into profoundly significant, emotionally charged visions. The milk delivery woman hadn’t changed; Hofmann’s perception of her had.
The Turn
Eventually, Hofmann’s terror began to subside. The experience shifted. He began to enjoy the visual distortions, the synesthesia (hearing colors, seeing sounds), and the sense of expanded consciousness.
He later wrote: “Now, little by little I could begin to enjoy the unprecedented colors and plays of shapes that persisted behind my closed eyes. Kaleidoscopic, fantastic images surged in on me, alternating, variegated, opening and then closing themselves in circles and spirals.”
This shift from terror to wonder characterizes many LSD experiences. Set (mindset) and setting (environment) profoundly influence the experience. Once Hofmann relaxed and felt safe, the same perceptual alterations that had terrified him became beautiful.
The Next Day
Hofmann woke the next morning feeling fine. His mind was clear, his body normal. He felt “a sensation of wellbeing and renewed life.” The world seemed especially beautiful—a common after-effect of LSD, sometimes called the “afterglow.”
Breakfast tasted extraordinary. He walked in his garden and perceived it with unusual intensity and clarity. Colors seemed brighter, natural forms more meaningful. This enhanced sensory appreciation lasted throughout the day.
Scientific Documentation
Hofmann documented his experience carefully. He had unintentionally discovered the most potent psychoactive substance known to science. His notes would become the foundation for LSD research.
Sandoz Pharmaceuticals saw potential. They began producing LSD for research, marketing it to psychiatrists and researchers as “Delysid.” The drug was seen as a potential breakthrough for psychotherapy and psychiatric research.
Medical Research Era
From the late 1940s through the early 1960s, LSD was intensively researched. Psychiatrists gave it to patients, researchers studied its effects on consciousness, and therapists explored its potential for treating alcoholism, depression, and anxiety in terminal patients.
Early results were promising. Some alcoholics showed remarkable improvement after LSD-assisted therapy. Patients with terminal cancer reported reduced anxiety and improved quality of life. Researchers mapped LSD’s effects on brain function, learning about neurotransmitters and consciousness.
Thousands of scientific papers were published. LSD research was legitimate, funded, and scientifically respected.
Cultural Shift
In the 1960s, LSD escaped the laboratory. Timothy Leary and others promoted LSD as a tool for spiritual exploration and consciousness expansion. The drug became associated with counterculture, anti-war movements, and social rebellion.
Media coverage became increasingly sensational. Stories of “bad trips,” flashbacks, and users jumping from windows (mostly exaggerated or false) created moral panic. Governments responded with increasingly strict regulations.
By 1968, LSD possession became illegal in the United States. Research became extremely difficult. By the 1970s, most legitimate LSD research had stopped. The promising medical investigations were abandoned.
Hofmann’s Perspective
Albert Hofmann never intended to create a recreational drug or fuel a social movement. He saw LSD as a tool for psychiatric research and understanding consciousness. He was dismayed by recreational misuse but also frustrated by research restrictions.
Hofmann remained convinced that LSD, used properly, had valuable medical and psychological applications. He advocated for resumed research while condemning irresponsible use.
He called LSD “medicine for the soul” and “my problem child”—a creation with enormous potential that had been both miraculous and troubled in its effects on society.
Bicycle Day Legacy
April 19 has become “Bicycle Day” in psychedelic culture, celebrating Hofmann’s famous bicycle ride. The date is observed by those who see psychedelics as tools for consciousness exploration or those simply appreciating the historical significance.
The bicycle has become a symbol in psychedelic art, representing the journey into altered consciousness. Hofmann’s ride through Basel represents the bridge between ordinary consciousness and psychedelic experience.
Modern Research Renaissance
After decades of prohibition, LSD research has resumed. Since the early 2000s, studies have investigated LSD’s therapeutic potential for:
- End-of-life anxiety in terminal patients
- Treatment-resistant depression
- PTSD
- Addiction
- Cluster headaches
Early results mirror the promising findings from the 1950s and ’60s. LSD appears to have genuine therapeutic applications when used in controlled settings with professional supervision.
Neuroscience research using modern brain imaging has revealed how LSD affects brain networks, providing insights into consciousness, perception, and mental disorders.
Hofmann’s Later Life
Hofmann lived to 102, dying in 2008. He remained active in advocating for psychedelic research throughout his life. In his later years, he saw promising signs that medical research might resume.
He took LSD occasionally throughout his life—always small doses, always in nature, always with respect for the substance’s power. His last intentional trip was reportedly on his 100th birthday.
Conclusion
Bicycle Day marks the moment when humanity discovered one of its most powerful tools for exploring consciousness. Hofmann’s accidental discovery and intentional self-experiment opened new territories of human experience and medical possibility.
LSD’s history has been turbulent: from promising medicine to countercultural sacrament to prohibited substance to, potentially, legitimate medicine again. Through all these transformations, Bicycle Day remains a fixed point—the moment when a Swiss chemist rode home on his bicycle and found that reality was far stranger and more malleable than he had imagined.
Hofmann’s laboratory notes from April 19, 1943, document a personal odyssey that would influence psychiatry, neuroscience, culture, and philosophy. His bicycle ride through Basel became a journey into unknown territories of human consciousness—a trip, in every sense of the word, that continues to resonate decades later.