Respiratory symptoms and diffuse pulmonary infiltrate developed in two patients under treatment for leukemia.Pneumocystis cariniipneumonia was suspected and then confirmed by open-lung biopsy in one and by percutaneous needle biopsy of the lung in the other. Both patients recovered promptly from the pneumonia during a 10- to 14-day course of treatment with intramuscularly administered pentamidine isethionate. In both patients hypoglycemia occurred during treatment, and subcutaneous abscesses at the drug injection sites developed in one patient.