A new long-acting repeatable injectable form of bromocriptine, (Parlodel LAR, Sandoz, Basle, Switzerland) has recently been developed. We studied the clinical, hormonal and radiological changes in six female patients with microprolactinomas and eight (3 female and 5 male) with macroprolactinomas receiving monthly injections of Parlodel LAR 50 to 100 mg for 6 months. Five patients with microadenomas and 4 with macroadenomas had normal prolactin (PRL) levels with Parlodel LAR 50 mg after one (5 patients), two (2 patients), or five (2 patients) injections; two patients with macroadenomas had normal or near normal PRL levels only after 4 monthly injections of 100 mg. Clinical improvement paralleled the changes in serum PRL. A complete normalization of a visual field defect occurred in one patient after 5 months of therapy. Marked shrinkage of the adenoma was shown by magnetic resonance and/or computed tomographical imaging in three patients with macroadenomas after 1 week. Side-effects were mild and usually transient. Parlodel LAR represents a novel treatment of hyperprolactinemic states which is both effective and well tolerated, and appears to be a useful alternative to oral therapy for long-term treatment.