In Tunisia, as in most african countries, Pneumocystis carinii pneumonia (PCP) is considered to be rare in HIV-infected patients. Frequencies of 8.6% and 21% have been reported. We examined 27 broncho-alveolar lavage specimens collected from HIV-infected tunisian individuals with respiratory symptoms over 4 years (1994-1997), by cyto centrifugation, Giemsa and Gomori-Grocott stain. Pneumocystis carinii (P carinii) was present in 9 cases, accounting for 33.3% of all specimens. Investigation of the reasons for the differences between african reports is necessary to establish appropriate therapeutic management. Technical difficulties of direct recognition of P carinii and selection bias may account for differences between african reports. However, differences still remain between the frequencies recorded in Africa and in other parts of the world, and recent advances seems to correlate this with geographical biodiversity of human-derived strains of P carinii and with differences in host ethnic background.