The efficacy, safety and tolerability of a single bromocriptine-LAR injection (50 mg) and of a 6 injection course at 28-day intervals, were evaluated respectively in 13 and in 9 hyperprolactinemic women with radiological signs of PRL-secreting pituitary adenoma. The long-lasting repeatable formulation of bromocriptine induced a rapid and prolonged hypoprolactinemic effect. Side effects related to central activity of the compound were observed only on the first day of compound administration in all subjects except one, whereas no modifications of cardiologic and haematologic parameters were observed. In one subject the occurrence of side effects was observed also during the 6 injection course of treatment. A significant shrinkage of pituitary adenoma was observed at the second CT scan performed in 7 of the 9 subjects treated for 6 months with bromocriptine-LAR. CT scan was not performed in one subject who achieved pregnancy after second bromocriptine-LAR injection, whereas unmodified size of pituitary microadenoma was found in one subject whose PRL secretion did not decrease during the treatment and who referred severe side effects.