The effects of alpha- and beta-adrenergic blocking agents on the serum prolactin levels of six women with hyperprolactinemia and galactorrhea were investigated. There was no indication that pituitary adenomas were etiologic agents for the hyperprolactinemia. Serum prolactin could be lowered with oral L-dopa. When intravenous phentolamine (an alpha-adrenergic blocking agent) or intravenous propranolol (a beta-adrenergic blocking agent) were administered for 1 hour, there was no significant change in serum prolactin levels.