Giant prolactinomas are rare pituitary tumors which have scarcely been reported in the literature. We describe three men with unusual presenting features of prolactin-secreting giant pituitary adenomas: prolonged and increasingly disturbing intolerance to light and noise; strange behavior and mood disturbances; and rhinorrhea followed by a finding of cerebrospinal fluid leakage. Treatment with dopamine agonist alleviated all symptoms, with concomitant suppression of plasma prolactin levels and a significant reduction in tumor mass. These cases emphasize the importance of considering unusual symptoms in the differential diagnosis of giant prolactinomas and the effectiveness of medical treatment.