Molecular typing was used to examine surveillance definitions for recurrent Clostridium difficile-associated diarrhea. Among 102 patients, 85 had a second episode within 8 weeks, 88% of which were relapses. Of 49 second episodes occurring after > 8 weeks, 65% were relapses. Categorization of a recurrent episode occurring after >8 weeks as a new infection may misrepresent the majority of episodes for surveillance.