From 1994 to 1998 the incidence of Clostridium difficile-associated diarrhoea (CDAD) in the Department of Geriatric Medicine, Huddinge University Hospital increased from 0.5% to 2.2% of all admissions. Corresponding figures for the whole hospital were 0.3% and 0.6%, respectively. The increase in CDAD at the Department of Geriatric Medicine was parallel with a more than doubled consumption of antibiotics. All geriatric patients with CDAD had been treated with antibiotics before onset of diarrhoea. Out of the antibiotic prescriptions 48% were a cephalosporin (mainly cefuroxim). In a matched reference group of geriatric patients 51% had been treated with antibiotics during the hospital stay. The patients with CDAD spent 27 +/- 14 days in hospital as compared to 13 +/- 9 days (P