Diarrhea is common in patients infected with the human immunodeficiency virus (HIV) in Africa. There has been speculation that HIV itself may cause some of the enteropathy seen. The intestinal secretory IgA (sIgA) response was used to evaluate HIV intestinal infections in Zambian patients with acute and chronic diarrhea. sIgA was extracted from stool specimens and evaluated by an ELISA. Seven (58%) of 12 HIV-positive patients with acute diarrhea and 25 (69%) of 36 HIV-positive patients with chronic diarrhea showed an sIgA response to HIV p24, compared with 1 of 10 HIV-positive patients without diarrhea (P < .025 for acute and P < .001 for chronic diarrhea). The mean duration of diarrhea was significantly longer in patients showing an anti-p24 response. An sIgA response to HIV antigens occurs commonly in infected patients with diarrhea and may provide further evidence of an etiologic role of HIV in the diarrhea associated with AIDS.