Background: Clostridium difficile is the main agent causing antimicrobial associated nosocomial diarrhea. Chronic renal failure is a risk factor for this type of diarrhea. Aim: To study the incidence and complications of Clostridium difficile diarrhea in a university hospital and among patients with renal diseases. Patients and methods: Retrospective review of all cases of Clostridium difficile diarrhea that occurred in a university hospital, between June 2000 and May 2001. Results: In the Nephrology Unit, 48 episodes of Clostridium difficile diarrhea occurred in 35 patients (7 cases per 100 discharges/year). This figure is higher than the global incidence in the hospital (0.53 cases per 100 discharges/year, p <0.001). The mean age of the 33 patients with renal diseases was 63 years old and 17 of them were female. Their main diagnoses were chronic renal failure in hemodialysis in 48%, uremic syndrome in 36% and renal transplant in 6%. Seventy nine percent had a history of antimicrobial use (42% quinolones and 36% cephalosporins). In 3 patients, the only risk factor was chronic renal failure. Seventy five percent responded to metronidazole and in 27%, diarrhea recidivated, compared with a 6% recurrence rate in other units, p <0.02). Eight patients died during hospital stay. Conclusions: Among patients with renal diseases, Clostridium difficile is frequent and associated with a high recurrence rate and mortality. Chronic renal failure may be a risk factor for its development (Rev Méd Chile 2003; 131: -).