A case is herein reported of pneumocystis carinii pneumonia in a 60-year-old female patient with ectopic production of ACTH at a position 2 cm superior to her right clavicle, revealed in an octreotide scan. Her extremely high plasma ACTH and cortisol levels (460 pg/ml and 80 microg/dl, respectively) were markedly decreased with the combined treatment of octreotide (300 microg/d) and ketoconazole (600 mg/d). As her serum cortisol concentration decreased, pneumocystis carinii pneumonia occurred on the third day of treatment. A secondary E. coli infection was superimposed and the patient died of disseminated intravascular coagulation and adult respiratory distress syndrome. This case suggests that primary prophylaxis for pneumocystis carinii infection should be initiated before cortisol lowering therapy, especially when the plasma cortisol concentration is excessively high, and that early adjunctive glucocorticoid therapy can reduce the acute mortality in patients with endogenous Cushing's syndrome and Pneumocystis carinii pneumonia. This case study would also like to point out that plasma ACTH and cortisol levels were decreased effectively by the combination of octreotide and ketoconazole in this instance of ectopic ACTH syndrome.