Dr. Hilary Koprowski is the pioneer of live polio vaccine, the first researcher to advance the diagnostic and therapeutic use of monoclonal antibodies, and the developer of the gold standard rabies vaccine. A world-reknowned maverick in biomedical research, Koprowski's research methods were often considered controversial and even radical. Nonetheless, he acquired key positions in many research organizations, such as the Rockefeller Foundation, Lederle Labs, and Wistar Institute, initiating landmark studies from cancer research to multiple sclerosis. One of his crowning achievements, the successful crusade for monoclonal antibodies, resulted in his founding of Centocor, a forerunner in the corporate world of biomedicine. This account of Koprowski's life history is a mixture of personal interviews, anecdotes, and legends of the art and science behind the man.