We collected clinical and microbiological observations, as well as follow-up on human immunodeficiency virus (HIV)-infected patients with bacterial pneumonia, and compared pneumococcal pneumonia in patients with and without HIV infection. Fifty five HIV-infected patients, who had had 68 episodes of bacterial pneumonia, were studied prospectively. Twenty one HIV-infected patients with pneumococcal pneumonia were compared to 69 non-HIV-infected patients with pneumococcal pneumonia. Aetiological diagnosis was established in 48 cases (71%). The most common causative agents were S. pneumoniae and H. influenzae. Sixty percent of episodes took place in asymptomatic carriers of HIV infection and 37% in acquired immune deficiency syndrome (AIDS) patients. Overall mortality was 10%. Fifty five percent of patients with follow-up had recurrent episodes. Bacteraemic pneumococcal pneumonia was more frequent in HIV- than in non-HIV-infected patients, and the mortality of pneumococcal pneumonia was also higher in HIV- (19%) than in non-HIV-infected (4.3%) patients. We conclude that bacterial pneumonia is a frequent problem in HIV-infected patients and that recurrent episodes are common. The clinical presentation of pneumococcal pneumonia is generally indistinguishable from that occurring in normal hosts, but bacteraemia is more common and the mortality is higher in HIV-infected patients.