The ganglion cell-containing tumors of the pituitary are rare lesions of undetermined histogenesis and nosology. A review of the literature revealed 42 such tumors, including the 3 cases described below. On the basis of this review, the tumors were divided into two histologic groups, one consisting of both adenomatous and gangliocytic elements (32 cases), and the other of the gangliocytic component only (10 cases). The first group of tumors were more common in females (23 of 32 cases) and were often active endocrinologically (28 of 32 cases), and acromegaly was the most common manifestation (19 cases). The second group was also more common in females (7 of 10 cases) but was less frequently active endocrinologically (3 of 19 cases). We review histologic and immunocytochemical findings in these tumors and discuss their histogenesis. We propose that the term mixed pituitary adenoma-gangliocytoma be used for the first group and gangliocytoma for the second. The two groups should be kept separate until their histogenesis is better understood.