To the editor: Among the adverse effects of pentamidine, fatal acute pancreatitis has never been reported. We have seen this complication in two patients with the acquired immunodeficiency syndrome treated with pentamidine for Pneumocystis carinii pneumonia. We report here the more illustrative case. A 27-year-old woman was hospitalized with interstitial pneumonia. At admission she was afebrile; abdominal findings and results of hematologic studies were normal. Bronchoalveolar lavage was positive for P. carinii pneumonia, and therapy with trimethoprim-sulfamethoxazole (20 and 100 mg/kg body weight · d, respectively) was started. Despite initial improvement, her temperature rose to 40.5 °C after 3 weeks,