A consecutive series of 82 acromegalic patients who underwent transsphenoidal surgery during a 5-year period is presented. Preoperative and postoperative values for human growth hormone (HGH) were available in 80 cases. Microadenomas were present in 18 patients with a mean preoperative HGH value of 25.2 ng/ml, diffuse adenomas in 39 patients with mean of 53.8 ng/ml, and invasive adenomas in 25 with mean of 68.0 ng/ml. There was no operative mortality. The results reflected the classification of the tumors, with apparent cures accomplished in 87.5% of previously untreated patients with microadenoma, all of whom had anterior pituitary function preserved. The percentages of apparent cures in cases of diffuse adenoma (68%) and invasive adenoma (54%) were much less satisfactory. Transsphenoidal microsurgery is capable of achieving good results, particularly in patients with microadenoma.