Bronchoalveolar lavage (BAD cell differentials and T-lymphocyte subpopulations were analysed in 95 HIV-infected patients with pulmonary symptoms to determine whether the type of cellular inflammatory response could be useful in diagnosis or as a prognostic marker. Patients withPneumocystis cariniipneumonia (PCP) had more BAL fluid lymphocytes, mainly comprising CD8+ cells, and patients with bacterial infection had more neutrophils than other patients. Neither of these changes were mirrored in peripheral blood. Seven patients who died after their acute episode of PCP had significantly higher BAL fluid neutrophils than 53 patients with PGP who survived (P= 0.002). There seems to be correlation between BAL fluid neutrophilia, PCP and concomitant bacterial infection since four out of seven patients with a fatal outcome had coinfection with bacteria, whereas only one patient with PCP and bacterial coinfection survived (P= 0.0007).