The author performed anterior transposition of the inferoir oblique muscle to a point 1mm posterior to the lateral end of the inferior rectus insertion in 36 eyes of 36 cases of +3 inferior oblique overaction, and to the lateral end of the inferior rectus insertion in eight eyes of five cases of +4 inferior oblique overaction. Postoperatively, the eyes that have normal action of the inferior oblique were 36 eyes(81.8%). Only one eye was overcorrected and four eyes were undercorrected. The overcorrected one case developed a hypotropia in primary position. It appears that this anterior transposition of the inferior oblique muscle is effective weakening method of the inferior oblique muscle for the treatment of +3 to +4 overaction of inferior oblique muscle.