To evaluate the prevalence of adenovirus strains in human immunodeficiency virus (HIV)-positive patients and to investigate their possible role in the onset of diarrhea, a total of 103 stools from HIV-seropositive patients at various stages of infection and 200 stools from sex and age cross-matched control subjects were examined. Adenovirus prevalence was measured by ELISA as well as conventional and rapid cell culture techniques. Results were compared between patients suffering from diarrhea and those without diarrhea. Adenovirus prevalence was statistically greater in HIV-seropositive cases than controls (8.7%, 2.5%, respectively). No significant difference was found between HIV-positive patients with diarrhea and those without gastrointestinal complications (P > 0.05). However, a significant difference in adenovirus prevalence was found between HIV-positive patients with diarrhea and control subjects with diarrhea (P = 0.02). Although viral prevalence varied with the different stages of HIV infection, differences were not statistically significant. In conclusion, although current opinion considers adenoviruses to be no more than opportunistic pathogens, the results of this large-scale study do not exclude a potential reactivation of latent adenovirus in HIV infection and suggest that further effort should be directed to elucidating such a mechanism if it exists as well as investigating the specific role of certain adenovirus serotypes in provoking diarrhea during later stages of HIV infection.