To determine the prevalence of diarrhea and weight loss among human immunodeficiency virus (HIV)-positive patients, we reviewed the records of all patients attending the Harris County HIV Clinic during a 4-month time period. Diarrhea was considered persistent if it had been present for > 14 days or on two or more consecutive clinic visits. Weight loss was defined as moderate (5–10% reduction in weight) or severe (>10% reduction) when the present weight was compared with the weight found at the initial clinic visit. Records were reviewed for 1, 370 patients, of whom 12.2% complained of diarrhea (7.7% acute and 4.5% persistent). Diarrhea was more common among patients with a history of male-to-male sexual contact than in patients with other HIV risk factors (p < 0.003 for acute and p < 0.006 for persistent). The mean CD4 cell count was not significantly different in patients with or without persistent diarrhea (176 versus 212) or acute diarrhea (215 versus 212). Weight loss was reported in 25.2% of subjects (12.8% moderate and 12.4% severe). It did not correlate with CD4 count. Persistent diarrhea also was not associated with weight loss. Acute and persistent diarrhea were common among ambulatory HIV-positive patients, particularly in homosexual men. We did not identify a correlation among diarrhea, weight loss, and CD4 count. Thus, factors other than chronic diarrhea and immunosuppression appear to be responsible for weight loss in HIV-infected patients. © 1995, Raven Press, Ltd., New York.