Robert Koch went from an obscure country physician to be the discoverer of the etiology of anthrax, the inventor of the technique of pure culture bacteriology and with that to the isolation of the tubercle bacillus and its identification as the etiological agent of tuberculosis. These successes propelled him to world-wide glory. In his search for a cure for tuberculosis, he proposed that tuberculin was such a cure. Unfortunately this turned out to be false, and his continued advocacy was a fiasco. Nevertheless his formulation of the germ theory of disease transformed medicine and led to a remarkable series of successes that clarified the etiology of a large number of infectious diseases.