Discover the serendipitous story behind Bicycle Day—LSD’s accidental breakthrough, its historic first trip, and how April 19 became a countercultural celebration of psychedelics, wellness, and the mind’s mysterious potential.
KEY TAKEAWAYS
-
What is Bicycle Day, and why is it celebrated?
April 19, 1943 marks the day Albert Hofmann intentionally took the first acid (LSD) trip—and biked home through Basel, Switzerland, forever changing neuroscience, mental health, and psychedelic culture. It's considered the beginning of psychedelic research and celebrates a deeper curiosity about consciousness.
-
Who was Albert Hofmann, and what did he discover?
Albert Hofmann was a Swiss chemist who discovered LSD-25 in 1938. On April 19, 1943, he became the first person to intentionally ingest it, leading to a deeply introspective and hallucinogenic experience that he later called "a wonderful, difficult, and strange journey."
-
Why does Bicycle Day (April 19) matter?
It commemorates the conscious journey into the psychedelic experience that was instrumental in sparking renewed research into consciousness, psychopharmacology, and psychedelic-assisted therapy.
-
Why is LSD being studied again?
LSD and other psychedelics, like psilocybin, are being researched for their potential to treat depression, PTSD, addiction, anxiety, and more—often with greater efficacy than traditional treatments.
Bicycle Day is a celebration of the first intentional LSD trip, taken by Dr. Albert Hofmann on April 19, 1943.
It marks the beginning of psychedelic science and symbolizes a turning point in our understanding of consciousness, perception, and mental health.
Here's what really happened, why it still matters, and how it's shaping the future of medicine and personal transformation.
The accidental discovery that changed everything.
In 1938, Albert Hofmann, a Swiss natural products chemist, was working at Sandoz Laboratories, developing derivatives of ergot—a fungus found on rye. He synthesized lysergic acid diethylamide, or LSD-25, hoping it might stimulate circulation and respiration, but it was shelved after initial tests were inconclusive.
INSPIRED BY NATURE
Lysergic acid diethylamide (LSD) is a semisynthetic product of lysergic acid, a natural substance from the parasitic rye fungus Claviceps purpurea. Albert Hofmann accidentally synthesized it in 1938 while searching for derivatives of lysergic acid to create a respiratory and circulatory stimulant.
Five years later, Hofmann felt a strange pull toward revisiting the compound.
On April 16, 1943, while working with the substance again, he accidentally absorbed a small amount through his skin and became the first person in history to experience an LSD trip.
He went home and experienced what he described as visions of "fantastic pictures, extraordinary shapes with intense, kaleidoscopic play of colours."
The ride that started a movement.
Three days later, when his Sandoz colleagues could offer no explanation, Hofmann decided to self-experiment.
Curious about what had happened, Hofmann decided to take a deliberate dose of LSD-25 to experience its effects more consciously, unaware at the time that what he thought was a small dose was, in fact, rather large.
So, on April 19, 1943, he ingested 250 micrograms of LSD—a dose far beyond the threshold amount—and began to feel its intense effects.
Between one and two hours later, Hofmann experienced slow and gradual changes in his perception. He asked his laboratory assistant to escort him home and, as was customary in Basel, they made the journey by bicycle. (Because of wartime restrictions, cars were banned in the streets of Basel.)
On the way, Hofmann's condition rapidly deteriorated; he struggled with feelings of anxiety, alternating in his beliefs that the next-door neighbor was a malevolent witch, that he was going insane, and that the LSD had poisoned him.
When the house doctor arrived, however, he could detect no physical abnormalities, save for a pair of widely dilated pupils. Hofmann was reassured, and soon his terror began to give way to a sense of good fortune and enjoyment, as he later wrote:
"...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, exploding in colored fountains, rearranging and hybridizing themselves in constant flux..."
In his notes, Hofmann described time warping, synesthetic visuals, and extreme shifts in perception. What began as a scientific inquiry became a seminal moment in the modern study of consciousness.
That bike ride, the first trip under the influence of a mind-altering substance, became immortalized as “Bicycle Day.”
DID YOU KNOW?
The term trip was first coined by US Army scientists during the 1950s when they were experimenting with LSD.
April 19's modern cultural significance.
The events of this first LSD trip, now known as "Bicycle Day," proved to Hofmann that he had indeed made a significant discovery: a psychoactive substance with extraordinary potency, capable of causing significant shifts of consciousness in incredibly low doses.
DID YOU KNOW?
Hofmann foresaw the drug as a powerful psychiatric tool; because of its intense and introspective nature, he could not imagine anyone using it recreationally.
Beyond its historical novelty, Bicycle Day, or April 19, represents the first intentional exploration of an altered state of consciousness with a synthesized psychedelic (not to be confused with natural psychedelics, which indigenous healing traditions have been using for millennia).
It marks a turning point in modern medicine, where chemistry, mysticism, and Western psychiatry began to overlap.
Albeit inadvertently, Bicycle Day laid the groundwork for decades of clinical research on LSD’s potential for treating depression, anxiety, PTSD, and addiction.
Today, LSD and other psychedelics like psilocybin and MDMA are being studied for their ability to enhance neuroplasticity, increase openness, and reduce activity in the brain’s default mode network—the seat of the ego.
As researchers and psychonauts continue to explore these effects, April 19 has taken on a deeper resonance.
It’s no longer just about LSD—it’s about consciousness itself.
How is Bicycle Day celebrated?
Bicycle Day is not a mainstream holiday—but in psychedelic communities, it’s marked with intention.
Some use it as a day for guided journeys, microdosing, journaling, or group integration. Others attend events, art installations, or underground gatherings where visionary art and music create safe, ceremonial containers for exploration.
For those choosing to take a substance on Bicycle Day, many approach it as a form of psychedelic communion—with self, with nature, or with the unknown.
Bicycle Day vs. World Bicycle Day.
Although they sound similar, they celebrate very different things.
Bicycle Day (April 19) honors Albert Hofmann’s legendary acid trip and the psychedelic revolution it sparked.
World Bicycle Day (June 3) was established by the United Nations to recognize the bicycle as a clean, sustainable mode of transportation.
In other words, one celebrates the bike as a vehicle for the soul. The other? For the body.
