This report describes a rare case of a patient with growth hormone (GH)-secreting pituitary adenoma with malignant transformation resulting in multiple metastases to the dura mater of the cerebral convexity and high cervical spine. The patient was a 60-year-old man with a previous history of pituitary adenoma with suprasellar extension who had undergone transsphenoidal surgery, craniotomy for a convexity tumor, and suboccipital craniotomy for a cerebellar tumor. Thirteen years after the initial surgery, suboccipital craniotomy for a cervicomedullary junction tumor and cervicospinal surgery for a metastatic tumor was performed. Histologic findings of resected specimens demonstrated that the primary pituitary tumor was typical adenoma (similar to specimens from the initial surgery) but that the cerebellar and the dural tumor from the high cervical spine had a high incidence of mitotic figures, and cellular anaplasia with nuclear polymorphism and necrosis. In addition, the serum levels of GH were noted to have decreased with recurrence of the tumor. It was concluded that patients with pituitary adenoma, even when benign, must be carefully followed for signs of malignant transformation, and spinal or distant metastases.