Eighteen cases of invading pituitary adenoma were removed via the approach of transsphenoidal microscopical operation. Among them 4 cases had insulin dependent diabetes. The pituitary adenoma were near-totally removed in 15 cases, partially removed in 3, and 10 cases were treated by supplement radiotherapy postoperatively and 5 cases by oral bromocriptin postoperatively. The average time of follow-up was 3.8 years. There were 3 cases(16.6%) had postoperative recurrence of the tumor which were finally cured by transfrontal craniotomy. The feasibility of the transsphenoidal microscopic approach for the invading pituitaty adenoma was discussed.