BACKGROUND We wanted to evaluate the very long-term effects of bromocriptine on prolactin (PRL) levels and pituitary tumor size in a large cohort of hyperprolactinemic patients. METHODS We conducted a retrospective cohort study in the Department of Endocrinology from Necker Hospital in Paris, France. Two hundred and forty-six patients consulted primarily for menstrual disorders, with diagnosis of hyperprolactinemia. Patients were followed-up for 99.9+/-3.6 months. One hundred and ninety-one were treated with bromocriptine, 32 underwent surgery, and 23 received no treatment. RESULTS The mean initial plasma PRL level was 135.0+/-20.2 ng/ml. Presence of an adenoma was detected in 60% of our patients and comprised a microadenoma in 64% of cases. Compared to oligomenorrheic women, amenorrheic patients had significantly higher levels of PRL and larger pituitary tumor size. In the bromocriptine group, PRL levels decreased from 99.6+/-7.9 to 20.0+/-1.5 ng/ml (p=0.00001). The medical treatment was associated with disappearance of the adenoma in 45% of the women and with stabilization of pituitary tumor size in 40% of patients. Surgery led to disappearance of the adenoma in almost all cases, but failed to definitively cure hyperprolactinemia. CONCLUSIONS In this large-scale retrospective study, the medical treatment of mild hyperprolactinemia was shown to be effective and sufficient after 9 years of follow-up.