Although the incidence of pneumonia after kidney transplantation is the lowest among all solid organ transplants, it is associated with high mortality rate (40-50%). We evaluated the efficacy of a protocol consisting of bronco-alveolar-lavage (BAL) for early microbiological diagnosis, reduction of the immunosuppressive therapy, and prompt administration of standardized antibiotic regimen in renal transplant recipients with severe pneumonia. Between 6/1989 and 5/1999, 40 kidney transplant recipients developed 46 episodes of severe pneumonia (hypoxia and/or infiltrate on the chest X-ray). According to protocol, in all these cases, a BAL was immediately performed and empirical antibiotic therapy was initiated with erythromycin and trimethoprim-sulfamethoxazole i.v. Furthermore, the immunosuppressive therapy was drastically reduced. Analyses of BAL fluid included cell differential count, cytopathologic examination and cultures for bacteria, fungi and viruses. Within 48 h, the therapy was switched to proper i.v. antibiotics, if necessary, according to the results of sensitivity testing of BAL specimens. The mortality rate was 12.5% (5 of 40). Mechanical ventilation was required in 20 cases (34.5%) and four of the patients that required intubation died. BAL alone established a diagnosis in 67.4% (31 of 46) of the patients. Bacteria were responsible for 61% of the episodes, with fungi responsible for 29% and viruses for 10%. Seven cases of Pneumocystis carinii pneumonia were treated with the prolongation of the initial therapy. We conclude that a combination of early detection of the responsible pathogen by BAL, aggressive reduction of the immunosuppressive therapy and the immediate empirical administration of erythromycin and trimethoprim-sulfamethoxazole is an effective strategy to treat pneumonia kidney transplantation (KTX) recipients.