To investigate the effect of hyperprolactinemia (HPLN) on bone mineral density (BMD), 21 previously treated hyprolactinemic amenorrheic women and 16 healthy, normally menstruating women were studied. Dualphoton absorptiometry was employed to specifically measure BMD at several sites in each of these women. Serum prolactin (PRL) along with LH, FSH, and estradiol (E₂) had been measured by radioimmunoassay before treatment. Although all measured sites (vertebral body femur neck, Ward's triangle, and trochanter) showed lower BMDs in the study control group, only BMD at Ward's traingle, but no at the three other sites, was noted to be statistically significant in the study group compared with the control. There was no significant correlation between BMD and the patient's age, duration of amenorrhea, E₂, and prolactin levels. Difference in BMD according to therapeutic modality was analyzed in these patients after treatment: transsphenoidal adenodectomy (TSA) with or without subsequent bromocriptine (Bx) (TSA ± Bx) proved better in preserving BMD than TSA combined with postoperative radiotheraphy (RT) and Bx (TSA+RT+Bx), or Bx alone.