Almost 40 percent of all pituitary adenomas are non-functional. Radiologically they appear like other adenomas and the definitive diagnosis is based on the endocrinologic and the histopathologic findings. In these tumors which necessitates close collaboration of neurosurgeons and endocrinologists, controversies still exist in treatment and follow-up modalities. In the Neurosurgery Department of Haydarpaşa Numune Training and Research Hospital, between January 1994 and September 1999, 41 patients were operated on for pituitary adenomas, 16 of those which were non-functional are presented here. 14 out of 16 cases were operated on by transsphenoidal ivme. and 2 cases by transcranial and transsphenoidal combined surgery. In patients operated on by transsphenoidal rolde the sucess rate was 85 %. In one of two patients operated on combined surgery the tumor removal was total, wheras in the second one the adenoma could only be partially removed. Hormonally non-functional adenomas most be followed-up carefidly and operated on when they present with mass effect. Transsphenoidal surgery is an effective and secure way of treatment in selected cases wheras in others, transcranial and combined surgery may be used. The results are discused in the light of the literature.