Environmental studies were performed in a hospital outbreak of Clostridium difficile-associated diarrhoea. Transmission was associated with the sluice room and the storage room where medical equipment was found to be contaminated with C.difficile. Typing of isolates by antibiotic-susceptibility patterns and profiles of EDTA-extracted proteins showed the presence of an "epidemic" strain common to the majority of patients and environmental sites. Control of the outbreak was achieved by improvement of environmental hygiene and use of disposable equipment.