In order to determine bowel patterns and perceptions of diarrhea and constipation in young adults not seeking health care, we surveyed 1128 young adults about their bowel habits. The mean number of stools varied by race and sex. Whites reported more frequent stools than nonwhites (7.8 vs 6.0 stools per week, P less than 0.0001) and men reported more frequent stools than women (9.2 vs 6.7 stools per week, P less than 0.0001). Milk and coffee consumption differed by race and sex, but did not account for the differences in stool frequency. Subjects were asked to estimate the percentage of the time their stools were normal or abnormal. The median value for normal was 85% of the time; only 3.6% of subjects reported diarrhea greater than 25% of the time, and only 7.3% reported constipation greater than 25% of the time. Subjects most commonly defined constipation as straining and hard stools and diarrhea as loose/watery stools and urgency. Investigators should use race- and sex-specific norms to study individuals who have patterns which deviate from the usual. Investigators and clinicians must also consider definitions used by their subjects.