A 13-year-old Japanese boy with pituitary prolactinoma whose growth had been retarded for more than 2 years was treated with bromocriptine alone for 140 weeks. After treatment, the serum level of prolactin, which was 1200 ng/ml before treatment, returned to normal and the pituitary tumour seen on the initial brain MRI had rapidly decreased in size after 16 weeks of treatment. Thereafter, his height improved (from -2.1 to -1.7 SDS). Conclusion:the favourable response obtained in this patient implies that bromocriptine monotherapy can be an effective first-line treatment for children with prolactinoma.