Dubos’s classic biography of Louis Pasteur, originally published in 1960 and for several years out of print is once again made available in this new and expanded hardcover edition. The original work has been enlarged by more than forty illustrations and tables, a new biographical sketch of Dubos, a glossary of technical terms and a chronological outline of Pasteur’s career. The book’s enduring appeal is a tribute both to its subject and to its author. Few scientists so captured the public imagination as Louis Pasteur, and fewer still had such a dramatic effect on everyday life. Dubos, a Pulitzer prize winner, was a modern biographer almost ideally suited to the task. A distinguished French-born microbiologist of broad culture, Dubos had a deep appreciation for the power and enduring significance of Pasteur’s scientific work. To the more personal dimensions of the biographer’s task, Dubos brought his keen insight into the wellsprings of human action, behavior, and personality. He thus appreciated the full range of Pasteur’s life, including its philosophical, religious, and political dimensions. Finally, Dubos’ graceful writing style allowed him to convey the excitement and significance of even the most technical aspects of Pasteur’s work.