Risk factors that influence the recurrence of nosocomial Clostridium difficile-associated diarrhea (CDAD) were determined in an 18-month follow-up study in a subacute geriatric department. A case-control study was conducted, comparing 43 patients with recurrent C. difficile-associated diarrhea (RCDAD) (case patients) with 38 patients who had only 1 episode of CDAD (control patients). The mean age of patients was 81.6 +/- 7.2 y (range 64-95 y). All cases with CDAD were receiving antibiotic therapy. RCDAD occurred in 53.1% of patients. Risk factors for RCDAD included fecal incontinence (p < or = 0.04), longer duration of fever from admission until first episode of CDAD (p < or = 0.02) and H2-antagonist treatment (p < or = 0.02). This study shows that RCDAD is a common clinical event in elderly hospitalized patients and may be predictable in some groups of patients.