A double blind, double dummy study on the efficacy, tolerability and safety of Parlodel LAR versus oral Parlodel was carried out in 13 hyperprolactinemic women. Six patients received active from of Parlodel LAR (1 intramuscular injection at a dose of 50 mg) and placebo for oral Parlodel simultaneously. Seven other patients received active form of Parlodel orally (up to 7.5 mg daily) and placebo for Parlodel LAR injection. In all patients the marked reduction in serum prolactin level was observed. In normalization of prolactinemia was achieved in 8 patients (2 LAR, 6 oral). Galactorrhea disappeared in 7 of 8 patients (4 LAR, 3 oral), menstrual bleeding occurred in 5 of 10 amenorrheic patients (3 LAR, 2 oral). Tumor shrinkage was shown in 1 case (oral therapy). The improvement of slightly narrowed visual field was documented in 3 cases (2 LAR, 1 oral). The adverse effect during the therapy were mild and transient. We conclude that both froms of bromocriptine are very useful for treatment of hyperprolactinemia but Parlodel LAR is better tolerated and more convenient in application because of its prolonged activity.