Pheochromocytomas may occur as either sporadic or familial tumors. Clinical features of pheochromocytomas in neurofibromatosis 1 (NF1) patients are similar to those in patients with sporadic pheochromocytomas, unlike pheochromocytomas associated with other hereditary syndromes. Here we report two cases of pheochromocytoma associated with NF1. Case 1: A 29-year-old man with previously undiagnosed NF1, was admitted to our hospital for hypertension and a right adrenal tumor. On physical examination, café-au-lait spots and neurofibromas were observed on his body. Serum and urine catecholamine levels were markedly elevated. Case 2: The patient was a 46-year-old man with NF1. The tumor was incidentally detected by ultrasonography. Serum and urine catecholamine levels were similarly elevated. 131I-MIBG scintigraphy showed an abnormal accumulation in the right adrenal gland. After this diagnosis of pheochromocytoma associated with NF1, open adrenalectomy was performed. No evidence of malignancy was seen in either case.