An audit ofPneumocystis carinüpneumonia prophylaxis used in HIV‐infected patients within Bloomsbury health authority in 1989 was carried out. A total of 134 patients who were prescribed 167 courses of PCP prophylaxis, with a variety of different regimens, was included in the study. Fifty three patients were prescribed 60 courses of primary prophylaxis, 55 of which were given with concurrent zidovudine. Eighty two patients were prescribed 107 courses of secondary prophylaxis, 96 after one episode of PCP and 11 after two episodes.Patients given primary prophylaxis, together with zidovudine, had a lower incidence of PCP than patients receiving no treatment. With secondary prophylaxis, a higher rate of relapse was seen with nebulised pentamidine than with co‐trimoxazole (16 per cent compared with 4.5 per cent). The incidence of adverse effects with co‐trimoxazole was higher in secondary than in primary prophylaxis. Compliance with nebulised pentamidine therapy was poor. Compliance with oral therapy was not mon