George Rathmann is to the entrepreneurial world what Willie Mays is to baseball: a no-debate, first-ballot Hall of Famer. The prescription drugs Rathmann developed at his two start-up companies still produce annual sales of some $9 billion.

Amgen, his first start-up, led the initial biotechnology boom in the 1980s and still rides the two drugs Rathmann coaxed out of scientists a quarter of a century ago: the anemia treatment Epogen and the cancer drug Neupogen, which (including associated drugs) have combined annual sales of more than $7 billion. Rathmann's other notable start-up, Icos, developed the erectile-dysfunction drug Cialis, which now generates annual sales of almost $2 billion for Eli Lilly.

Rathmann died in Palo Alto, California, on April 22 of complications from kidney failure. He was 84.

A Ph.D. in chemistry, Rathmann joined 3M in 1951. According to his son, Rick, Rathmann wanted to be CEO of 3M and, when that seemed unlikely, jumped to Lytton Industries, where he had a brief and difficult tenure. He next joined Abbott Laboratories, and through the 1970s led research and development in its diagnostics unit.

So far, Rathmann sounds like a corporate climber. But no. "He loved chaos," Rick Rathmann says. "He was always prepared to start over." Rathmann took a leave from Abbott in 1980 to study the emerging science of biotechnology. An investor group was doing the same, and together they launched Amgen later that year. They had no drug in development. No big idea other than exploiting the new technology.

Rathmann was cited in Good to Great as a fabulous hirer of talent, but his son says his greatest strength as a manager was actually in squeezing the best out of the people he had. Bearded and 6-foot-5, he was an imposing figure in the workplace. "He was a bugger--really hard to work for," says Rick. "He set the bar high for himself and everyone else. Top executives could cry."

Rathmann combined toughness with a familial approach to work: company parties, with spouses and kids, were often at his house. He and his wife, Joy, knew everyone's name. "He was a father figure," says Lowell Sears, a former Amgen CFO. Amgen began scattershot, chasing scientific leads all over, but Rathmann quickly narrowed the focus. Its two big drugs hit the market in 1989 and 1991.

Rathmann's energy, physical and intellectual, was legendary. Sears recalls a meeting over a complex financing deal: "George was also dictating an unrelated memo and solving a Rubik's Cube. He moved at incredible speed. It was exhilarating." After retiring from Icos, Rathmann ran a $40 million family foundation, oversaw his two sons in a venture capital fund, directly advised portfolio companies, and conjured up outlandish stories to tell his grandchildren.