Estrogen and progesterone receptor binding activity was measured in 22 intracranial meningioma surgical specimens. None of the tumors was estrogen receptor-positive, whereas 19 were progesterone receptor-positive. Of these 19 patients, all demonstrated significant computed tomographic (CT) evidence of peritumoral edema. None of the 3 patients who lacked progesterone receptor binding had CT evidence of peritumoral edema (P less than 0.005). Peritumoral edema associated with intracranial meningiomas seems to be related, at least in part, to progesterone binding activity. This implicates the potential use of progesterone antagonists for the treatment of incompletely resected or recurrent meningiomas.