Prolactinomas are the most common of hormone secreting pituitary adenomas. Patients with prolactinomas generally have a benign prognosis. An algorithm is currently available for managing of this disease. Giant prolactinoma larger than 40 mm with severe invasive growth account for about 2—3% of the prolactin-secreting pituitary adenomas and evidence about management of such patients is limited. This case illustrates progress of a giant prolactin-secreting pituitary adenoma up to 70 mm in young male with a family history of prolactinomas in the absence of the adequate therapy for 8 years after initial diagnosis. After evaluation, it was decided to prescribe medical treatment. Cabergoline therapy started after evaluation appeared to be effective and had lead to significant decrease of serum prolactin level and shrinkage of pituitary adenoma. Described case emphasize the crucial role of identification of hyperprolactinemia among young patients on early stages of the disease. Our observation implies that treatment with dopamine agonists might be effective even in cases with giant prolactinomas.