Approximately 15 to 35% of patients with a first episode of Clostridium difficile-associated diarrhea relapse within 2 months. Between 1994 and 1997, strains from 93 hospitalized patients with C. difficile recurrences were fingerprinted by using both serotyping and PCR-ribotyping. The results showed that 48.4% of clinical recurrences were, in fact, reinfections with a different strain of C. difficile. Rates of clinical recurrences could therefore be reduced by implementing strict isolation precautions.