Abstract A study of 2856 Clostridium difficile -associated diarrhoea (CDAD) patients from 34 hospitals in Germany was carried out over a period of 12 months in 2007. The overall incidence of CDAD cases was 46.5 per 10,000 admitted patients, or 6.6 cases per 10,000 patient-days. Seventy-three percent of cases were considered to be nosocomial and 8.4% were classified as severe. There was a wide range in the incidence of CDAD between the hospitals (interquartile range [IQR] 3.2–9.2 cases per 10,000 patient-days), and the incidence of nosocomial cases (IQR 1.7–6.7 per 10,000 patient-days). The differences between the hospitals were in line with the differences in local diagnostic and infection control procedures. The overall incidence in the hospitals participating in the surveillance system was much higher than that in the discharge data from the whole of Germany in 2006. This may be due to more diligent ICD9 coding by the clinicians during an active surveillance strategy. However, the group of hospitals participating in the study was small and may not be representative of the situation in the country as a whole.