OBJECTIVE To determine the predictive factors for endocrinological remission of patients with growth hormone (GH)-secreting pituitary adenomas. METHODS In 47 patients with GH-secreting pituitary adenomas who underwent endoscopic endonasal transsphenoidal surgery with intraoperative GH measurements from 2002 to 2011, the relationship between the intraoperative GH levels and postoperative remission was analyzed, and 2 items that predicted remission (GH half-life obtained 30 minutes or less after removal and a minimum surgical GH level less than 2.5 ng/mL) were determined. In addition, 2 surgical observations (endoscopic confirmation of no tumor remnants and pathologic confirmation of the absence of tumor remnants in the bordering tissue) were also considered. Positive items resulted in one point, and scores ranged from 0 to 4. For 27 patients who underwent surgery from 2012 onwards, this scoring system was applied by 3 independent operators, and the remission rates and predictive values were estimated. RESULTS Twenty-six of the 47 (55.3%) patients achieved remission. The remission rates were significantly different for different scores. In the 27 patients treated from 2012 onward, repeat residual tumor examinations were performed if the GH score did not reach 2 at the end of the removal. Nine patients had final scores of 3 or 4. All of these patients achieved remission. In 16 patients with final scores of 2 or less, only 2 with Knosp grades of 0 and 1 achieved remission. CONCLUSIONS Our scoring system, which incorporated GH measurements and surgical observations, predicted postoperative remission. Complete tumor removal was critical to achieve intraoperative scores over 3.