This article describes the investigation that followed the reporting of four cases of Legionnaires' disease by the Sarlat Hospital to the Dordogne Departmental Health and Social Services Agency (DDASS). Between July 2002 and October 2002, 35 cases were reported to the DDASS, and six deaths were recorded among patients with Legionnaires' disease. A cooling tower at the hospital was contaminated and was disinfected.