BACKGROUND The aim of this study was to describe the characteristics of the infections by Pseudomonas spp. observed in patients with HIV infection in Spain. METHODS A retrospective study was performed of the isolations of Pseudomonas spp. in microbiologic samples of patients with HIV infection in three hospitals from Mallorca, Spain, since 1986. RESULTS Twenty-nine patients with some positive culture for Pseudomonas were reviewed. In 20 cases the infection presented in advanced stages of the disease when the patient fulfilled AIDS criteria. The most frequent foci in both community acquired and nosocomial infection was respiratory (16 and 3 cases, respectively). Fifty percent of the cases presented bacteremia. The classically described predisposing factors for infection by this germ were presented in 19 patients. Pseudomonas aeruginosa was the most frequently isolated type (22 cases). Only 5 patients received the appropriate treatment on admission. Clinical cure was achieved in 23 patients, with recurrence being observed in 10. Five patients died in relation to the infection. CONCLUSIONS Infections by Pseudomonas spp. in Spain appear to have increased in frequency in patients with HIV infection in the last decade. These infections appear in advanced phases of the disease and mainly involve the lung, with high rates of bacteremia and a high number of recurrence. Empiric treatment of patients with advanced HIV infection with suspicion of bacterial infection should include antipseudomonic drugs.