In the 1820s, some years after smallpox vaccination had been introduced by most German states, physicians were faced with a seemingly new disease that they called false smallpox or varioloid . The paper deals with two epidemics of varioloid that spread in Würzburg between 1825 and 1829. The reports of eyewitnesses, case histories, and patients records from the Julius Hospital in Würzburg are analysed with respect to the state of vaccination in this region, and in consideration of the personal, practical (...) and scientific interests of the physicians involved. Special points of discussion are Schoenleins concept of epidemic disease, the role of contagionism, and the ambiguity of historical diagnosis. (shrink)