PURPOSE: To examine changes in ocular torsion after the weakening procedure for the inferior oblique muscle in patients with overaction of inferior oblique muscle (IOOA). METHODS: Twenty-eight eyes that had undergone the graded IO anteriorization combined with recession were evaluated. Twelve eyes from 11 patients had IOOA due to superior oblique muscle palsy (SOP) and 16 eyes from 9 patients had primary IOOA. Fundus photograph was taken to examine changes in torsional deviation before and after surgery. RESULTS: The average torsional deviation decreased from +17.5 +/- 7.3 degrees before surgery to +6.4 +/- 5.8 degrees after surgery, with the amount of correction being 11.1 degrees. It was corrected by 12.6, from +19.1 +/- 7.7 degrees to +6.5 +/- 4.8 degrees, in patients with SOP, and by 10 degrees, from +16.3 +/- 6.9 degrees to +6.3 +/- 6.6 degrees, in patients with IOOA (p<0.05). CONCLUSIONS: About 11o excyclotorsional correction was observed in patients with IOOA after IO anteriorization combined with recession.