In 12 cases of pituitary apoplexy, a preexisting unsuspected adenoma was found. The initial manifestations were sudden onset of headache (12 patients), signs of meningeal irritation (10) with fever (four), altered consciousness (12), and ophthalmologic disturbances (eight). The diagnosis was retrospective in three cases. Radiologic investigations were always suggestive if carefully considered. The plain skull roentgenograms, in particular, showed an enlarged sella turcica in 11 cases. Three patients had prolactin adenomas, and nine had nonfunctional adenomas. Medical treatment was successful in only three patients; surgery was performed in 10 cases by means of a sublabial transseptal microsurgical approach. Postoperative neurologic complications were serious in two cases. Endocrine insufficiencies were common: eight cases of permanent panhypopituitarism, two cases of pluritropic anterior pituitary dysfunction, and three cases of persistent hyperprolactinemia.