Transsphenoidal adenomectomy was done on 125 acromegalics. A clinicomorphological study was performed on 113 of these patients. The distribution of morphological types of tumors was similar in both sexes. In the total group it was: sparsely granulated GH cell adenomas 52.8%, densely granulated 25.7%, mixed somatotroph and lactotroph adenomas 15.9%, plurihormonal adenomas 1.8%, acidophil stem cell adenomas 2.6%, and oncocytoma 1.8%. The GH plasma level in male patients was significantly higher than in female patients. In both sexes GH secretion was highest in patients with mixed GH and PRL cell adenomas followed by patients with densely granulated GH cell adenomas. Plasma PRL levels were significantly elevated in all males, except for those with densely granulated GH adenomas where prolactinemia was normal. The mean plasma PRL levels were also elevated in females with highest values in mixed somatotroph and lactotroph adenomas. The PRL levels in female patients with densely granulated GH cell adenomas are more elevated than in female patients with sparsely granulated GH cell adenomas.