In order to establish which are the most frequent endoscopic detectable colorectal disorders in AIDS patients with intestinal complaints we analysed 236 colonoscopies in a series of 186 patients. The colonoscopic procedure was always followed by biopsies, even in the absence of macroscopic lesions. The most frequent diagnosis was colitis due to citomegalovirus infection observed in 64 exams (27.1%) and presented with an inflammatory pattern with ulcers, followed by Cryptosporidium sp., found in 31 exams (13.1%). This infection, conversely, presented as an inflammatory non-ulcerative lesion. Others pathogens found in lower frequency were: Mycobacterium sp., Histoplasma capsulatum, Herpes simplex, Isospora sp., Giardia sp., Candida sp. and Campilobacter sp.. Neoplastic lesions, mostly Kaposy's sarcoma, were detected in 10 of the colonoscopies (4.2%). The most frequent colorectal disorders in AIDS patients detected by endoscopic procedures are citomegalovirus and Cryptosporidium infection. Biopsies are always necessary to confirm the endoscopic diagnosis and to identify the presence of associated pathogens.