Abstract: Max Schüller (1843–1907) was a German surgeon and microbiologist. From 1884 to 1905, he published histopathologic and bacteriological research on bacterial infection of human joints. Beginning in 1892, he focused on a bacterium he had identified in joints of patients with rheumatoid arthritis and surmised that he had discovered the cause of this disease. He persisted in conducting various experiments, some original at the time, with which he convinced himself of the validity of his discovery, without considering the possibility that he was working on contaminants. Contemporaneous attempts to confirm Schüller’s findings gave inconsistent results. A century of microbiological research with ever more sensitive techniques has not definitively answered the etiologic question. This history is a cautionary tale of the difficulty of disproving an erroneous premise.