Clostridium difficile-associated disease (CDAD) is primarily a nosocomial condition. Community-acquired disease has been reported but the incidence is felt to be low and the rate of disease resulting in hospitalization is reported as negligible. We recently experienced a 6-month outbreak of CDAD (January to June 1995): 139 patients were involved and four deaths were attributable to pseudomembranous colitis. Early in the outbreak period we were aware that many new admissions presented with C. difficile cytotoxin B positive diarrhoea: in some cases this was the sole reason for hospitalization. This observation forms the basis of this report.