Twenty-seven episodes of Pseudomonas aeruginosa bacteremia in 21 patients with AIDS were evaluated at the Mount Sinai Medical Center in 1987-1992. Of 21 primary episodes, 12 were acquired in the community, 8 were nosocomial, and one was acquired in a nursing home. Sources of bacteremia (i.e., sites of infection; n = 30) included the lungs (12 cases) an indwelling vascular catheter (9), and the upper respiratory tract (5, including 2 cases of sinusitis, 2 cases of malignant external otitis, and 1 case of epiglottis/pharyngeal cellulitis); in 4 cases the source was unknown. White blood cell counts ranged from 0.1 to 26.2 (mean, 4.32) x 10(3)/mm3; in 19 of 26 cases, the absolute neutrophil count was > 1 x 10(3)/mm3. With the exclusion of primary episodes of bacteremia that resulted in death, the rate of relapse was 33.3% (5 of 15 cases). Mortality for the 25 evaluable episodes of bacteremia was 40% (32% for primary infection and 80% for relapse; P = .06); 52.6% of evaluable patients (10 of 19) ultimately died of P. aeruginosa bacteremia. The institution of appropriate therapy at presentation did not positively affect outcome. Rates of response were higher among episodes treated with a drug combination (an antipseudomonal beta-lactam or monobactam antibiotic plus an aminoglycoside) than among those treated with a single agent (P = .036).