A prospective study of 22 women with hyperprolactinemia from various causes was performed with use of bromocriptine in nine patients and pergolide in 13 patients. The administration of 50 micrograms of pergolide followed by 100 micrograms on the second day showed significant decrements (p less than 0.01) in systolic and diastolic blood pressure in either standing or lying position. However, 25 micrograms of pergolide followed by 50 micrograms did not lower blood pressure. Both 25 and 50 micrograms of pergolide induced a maximal and significant (p less than 0.005) inhibition of prolactin at 8 hours and remained suppressed for at least 24 hours. Long-term treatment with either bromocriptine or pergolide was continued for 48 weeks. Both dopamine agonists demonstrated a similar degree of prolactin inhibition throughout time. However, only patients treated with pergolide had higher levels (p less than 0.05) of luteinizing hormone and follicle-stimulating hormone. Resumption of spontaneous menses and cessation of galactorrhea occurred at similar times in both groups. It can be concluded that either dopamine agonist can be safely given to patients with hyperprolactinemia.