To study enteropathogens, 100 fecal samples were collected from a Brazilian human immunodeficiency virus (HIV)-seropositive population, with or without diarrhea. Giardia lamblia and calicivirus were significantly associated with diarrhea as were severe immunosuppression and the presence of at least one enteropathogen. No sample was positive for rotavirus and only one asymptomatic individual carried the astrovirus. We concluded that there is a great diversity of pathogens and opportunistic infections in the studied population, with a high prevalence of mixed colonization/infection. Our findings pave the way for future molecular studies related to the expression of virulence factors and to the possibility of pathogen-pathogen interactions, especially between G. lamblia and calicivirus. These findings are relevant to the improvement of therapies and controlling diarrhea in the HIV-seropositive population.