A patient with acquired immune deficiency syndrome who developed symptoms of partial gastric outlet obstruction during the course of a severe diarrheal illness due to cryptosporidiosis is presented. Endoscopic evaluation of the stomach revealed an inflamed pyloric ring and channel with clinical evidence suggestive of partial outlet obstruction. The finding of cryptosporidial organisms on biopsy of the pylorus highlights the potential for diffuse gastrointestinal involvement by this parasite and offers an alternative explanation for the symptoms of nausea and vomiting associated with the diarrheal illness.