Bill Haast, who turned his childhood fascination with snakes into an exceptionally long career as a roadside showman, a supplier of venom and a man seemingly immune to the bites of cobras, vipers and other deadly snakes, died June 15 at his home in Punta Gorda, Fla. He was 100 years old.

His wife did not disclose the cause of death. It was apparently not related to the 172 bites he had received during a lifetime of handling poisonous snakes.

For decades, Mr. Haast (rhymes with “lost”) ran a Florida roadside attraction called the Miami Serpentarium, but he sought to transcend the inherently creepy nature of reptiles and be taken seriously as a visionary man of science and healing.

Even though he put on shows for tourists, his primary occupation was as the country’s leading producer of raw venom for use in snakebite serums. By the 1990s, he was providing 36,000 samples of venom to pharmaceutical laboratories each year.

He owned as many as 10,000 snakes at a time and had supplies of venom from 200 species of poisonous reptiles, including sea snakes, African tree snakes, cottonmouths, rattlesnakes, cobras, kraits, green mambas, tiger snakes and vipers from around the world. Grabbing the deadly snakes with his bare hands, Mr. Haast would squeeze their jaws open and allow their fangs to pierce a rubberized membrane, releasing drops of venom into a glass vial. It took thousands of repetitions to produce enough venom to be made into an antivenin.

Snakebites were a constant occupational hazard, leading Mr. Haast to adopt an unusual regimen of self-medication. In the 1940s — Sept. 18, 1948, to be exact — he began to inject himself with diluted amounts of cobra venom, which he gradually increased over time. He developed an immunity to most snakebites and became a staunch believer in what he considered the medical benefits of venom.

“It was risky, but I did it very cautiously,” he told the Tampa Tribune in 1997. “When I started in 1948, a doctor said he wouldn’t give me a nickel for me living two years. Well, I’m still here, but the doctor died of a coronary.”

He faced perhaps his most frightening challenge in 1954, when he was bitten by a blue krait, an Asian snake that is among the most highly poisonous in the world.

“I had never heard of a krait bite victim ever surviving,” Mr. Haast told the Associated Press in 1996. “I felt like the skin had been stripped from my body, like every nerve in my teeth was exposed, like my hair was being ripped out of my head.”

He hallucinated, with visions of lambs’ heads and purple curtains, but soon recovered and went back to work. The snake died 10 days later.

In time, Mr. Haast’s venom-enriched blood came to possess healing properties. Transfusions from his blood helped save the lives of more than 20 snakebite victims around the globe.

In the 1970s, a Miami doctor worked with Mr. Haast to develop medications from snake venom that were used to treat patients with multiple sclerosis, Parkinson’s disease, arthritis and other ailments. Despite compelling testimonials from patients, the treatments were later banned by the Food and Drug Administration.

Mr. Haast ate animal protein only on even-numbered days and seldom consumed refined sugar, but he was convinced that the true secret of his longevity came from his carefully controlled doses of venom. He remained fit and nimble well into his 90s, with an unusually youthful appearance.

In 1989, while Mr. Haast was being treated in Utah after being bitten by a Pakistani pit viper, a hospital spokesman couldn’t believe his age.

“Tell me,” he asked Miami Herald columnist Carl Hiaasen, “has he had a lot of plastic surgery or something? He’s a very young 78. He looks like he’s 30.”

William Edward Haast was born Dec. 30, 1910, in Paterson, N.J., and captured his first snake when he was 7. He dropped out of high school to be a snake handler in a traveling carnival and, in the 1930s, worked for an Everglades moonshiner. The job gave him ample opportunity to search the swamps for snakes.

He later became a mechanic and flight engineer for Pan American Airways and flew all over the world, often bringing back exotic snakes, he said, in his toolbox.

He began his work on the medical properties of venom in 1946 and, two years later, opened the Miami Serpentarium. Mr. Haast put on five shows a day, demonstrating how to extract venom from poisonous snakes. Pythons, iguanas, 400-pound turtles and crocodiles were on display, but after a 6-year-old boy was killed by a crocodile in 1977, Mr. Haast was disconsolate. He closed the attraction in 1984 and moved to Utah for six years.

His first two marriages ended in divorce. A son from his first marriage predeceased him.

Survivors include his third wife and longtime business associate, Nancy Harrell of Punta Gorda; two daughters from earlier marriages; three grandchildren; two great-grandchildren; and two great-great-grandchildren.

In 1990, Mr. Haast settled near the Florida Gulf Coast town of Punta Gorda, where he continued to draw venom from snakes for medical use. He was forced to retire at 92, when a bite from a Malaysian pit viper claimed his right index finger.

Well into old age, Mr. Haast injected a cocktail of venoms from 32 lizards and snakes.

“I could become a poster boy for the benefits of venom,” he told the Miami Herald in 2006. “If I live to be 100, I’ll really make the point.”