The authors reported a patient with a large prolactinoma (PRL 1,716 ng/ml) who was treated with bromocriptine for two years and followed up for a subsequent 36 months. After the start of the therapy, the tumor size was dramatically reduced, and finally the disappearance of the tumor was confirmed by high resolution coronal CT. The serum prolactin level and pituitary function were normalized. The tumor has not regrown and the blood prolactin level has remained normal for 36 months since the discontinuation of bromocriptine administration. This is a very rare case report on the eradicative effect of bromocriptine on such a large prolactinoma. Another characteristic of this case was that the prolactin reserve was maintained not only before the therapy but also during the early stage of the therapy.