Prolactin and pituitary gonadotropin levels were studied in eight patients with polycystic ovarian syndrome. All women were of reproductive age and had had menstrual disorders since menarche. Three patients had hyperprolactinemia with or without galactorrhea and tomograms of the sella turcica revealed pituitary microadenomas. The remaining five patients with normal baseline prolactin levels had a prolactin stimulation test which used 25 mg of thorazine per os, and a prolactin suppression test using l-dopa 500 mg per os. Analysis of the results of these tests and a comparison with tests performed in five normal individuals used as controls showed significantly different responses in the two groups of women. The preliminary information obtained indicates that an abnormal prolactin secretion status may exist in the polycystic ovarian syndrome.