Moyamoya disease associated with prolactin (PRL)-producing pituitary adenomas occurred in two females with elevated blood PRL levels (285 and 120 ng/ml). Computed tomography revealed cystic tumors extending from the sella turcica to the suprasellar cistern. Carotid angiography demonstrated stenoses or obstructions of the bilateral internal carotid arteries at their end point and development of bilateral basal moyamoya vessels. Histological diagnosis in one case was PRL-producing chromophobe adenoma. No stigmata of neurofibromatosis or any history of irradiation was found. Compression of carotid arteries by the tumor was unlikely. These cases should therefore be classified as moyamoya disease accompanied by brain tumor, a very rare occurrence. The hypothalamic disturbance caused by moyamoya disease may have induced the hyperprolactinemia, resulting in secondary prolactinoma.