The prevalence of infection with mycobacteria, both typical and atypical, is increasing along with prevalence of infection with HIV. Patients with pulmonary tuberculosis (PTB) and patients with chronic diarrhoea are forming a growing proportion of the patient population in hospitals in central Africa. To investigate the possibility that mycobacteria may be responsible for some of the HIV-related enteropathy seen in Lusaka, we studied 89 patients in four different diagnostic groups, clinically, by Mantoux test and by microscopy and culture of stool specimens for mycobacteria. In the HIV-positive group with chronic diarrhoea (n = 31), two patients were found to have mycobacteria on faecal smear and three were culture positive while of the 15 HIV-negative controls, three were smear positive and three were culture positive. Of the 15 patients with proven PTB, three had positive faecal smears but none were culture positive. In the fourth group of 24 patients with suspected PTB, seven were smear positive and five, culture positive. Only in this last group was there some correlation between smear results and culture results. Although this last finding is difficult to explain, it appears that there is no correlation between the symptom of chronic diarrhoea and the presence of mycobacteria in the stool. We conclude that mycobacteria do not play a significant role in the pathogenesis of HIV-related enteropathy in Lusaka.