The authors report a rare case of collision tumor composed of intrasellar gangliocytoma and pituitary adenoma. The patient was a 56-year-old woman, who had a mild acromegalic feature and slightly elevated plasma GH level. But she had no abnormal neurological findings. Transsphenoidal microsurgery was performed and an intrasellar tumor was totally removed. After the operation, plasma GH level decreased to within normal level. She was discharged with no neurological deficit. Histological examination showed two components. One of them was gangliocytoma composed of many large, and often binucleated cells with Nissl substance. The other had the appearance of chromophobe adenoma. In this part, some of the cells showed positive stain for GH. The clinical and histological features of this lesion are discussed and compared with 31 other cases of intrasellar ganglioglioma or gangliocytoma.