This paper reviews the safety data on bromocriptine administration for 1 to 10 years at daily doses of 1.25 to 80 mg in over 1100 patients with pituitary hormone overproduction (mainly from prolactinomas and growth-hormone producing adenomas), at daily doses of 3.75 to 170 mg in over 700 patients with Parkinson's disease, and at daily doses of 2.5 to 20 mg in 28 patients with various other conditions. In addition, information is provided on the safety for mother and child of bromocriptine administered at daily doses of 2.5 to 35 mg throughout gestation (54 pregnancies) or during its later stages (39 pregnancies). The side-effects of long-term bromocriptine treatment are usually no different from those seen during short-term treatment; most of them are relatively benign, and they have been shown in virtually all patients to be reversible. Bromocriptine appears to have no harmful effect on hepatic, renal, haematologic, or cardiac functions. It is considered that a hitherto unknown, severe though rare side-effect of bromocriptine is unlikely to be reported after such long experience.