A 41-year-old homosexual man complained about weight loss of 14 kg over a period of 6 months. He developed exertional dyspnea and fever up to 39.6 degrees C. The ESR was elevated and the fraction of immature neutrophils increased. Penicillin was administered with no effect, chest X-ray showed basal pulmonary infiltrates, P. carinii was found in bronchioalveolar fluid. HIV-serology was positive. Sulfamethoxazole/trimethoprim (1600/320 mg daily) and 100 mg of prednisolone/die led to reduction of fever. Prevention of P. carinii pneumonia relapse is currently underway with bi-weekly inhalation of pentamidine-isethionate aerosol.