The object of this case control study was to evaluate the frequency, the risk factors, the microbiological spectrum and the outcome of 249 episodes of Bacteraemia observed in 209 HIV-infected patients, most of them affected by AIDS. The rate of bacteraemia in the total yearly HIV-related admissions increased from 4% in 1985 to 13% in 1993. The more common aetiological agents of bacteraemia were: Staphylococcus aureus (29.7%), non-typhoidal species of Salmonella (14.1%), Staphylococcus epidermidis (10.9%), Streptococcus pneumoniae (8.4%) and Pseudomonas aeruginosa (7.6%). A mixed flora was found in 14% of the episodes. Multivariate analysis of predisposing factors indicated that a low CD4 + T-cell cell count (<0.2 x 10(9)/l) (P=0.01), use of central venous catheters (CVC) (P = 0.01) and a neutropenia (polymorphonuclear neutrophils 11.0 x 10(9)/l) (P=0.04) were independent risk factors for the development of bacteraemia. Logistic regression did not reveal any association of bacteraemia with intravenous drug abuse (on univariate analysis P=0.04). The response (31.8%). Recurrences to specific therapy was favourable in 170 episodes (68.2%); death occurred in 79 (31.8%). Recurrences arose in 40 patients, 27 (42.5%) of them died. The outcome of bacteraemia was influenced by a low number of CD4 + T-cells (P<0.001) but not of polymorphonuclear cells, Our findings suggest that bacteraemia is a relatively common event in HIV-infected patients especially under particular conditions (e.g. intravenous drug abuse, use of CVC, neutropenia and a low CD4 + T-cell count). It requires special attention from physicians who must recognise and treat the condition promptly at an early stage.