This paper presents a comparative study of the effectiveness of myectomy and anterior transposition in the treatment of inferior oblique muscle overaction. We operated 160 patients with overaction of the inferior oblique muscle. Eighty patients (148 eyes) were operated by myectomy at the insertion and 80 patients (151 eyes) by anterior transposition of the insertion of the inferior oblique near the temporal side of the insertion of the inferior rectus muscle. Comparison of the two methods, using the chi-squared test, showed that: 1) both surgical procedures were equally effective (chi 2 = 0.26) for correcting overaction of the inferior oblique muscle and V-phenomenon; 2) weakening of the inferior oblique muscle of both eyes was almost always required (in 115 out of 116 cases) in cases with V-phenomenon and often (24 out of 44 cases) in cases of congenital paresis of the superior oblique muscle. We conclude that both procedures are equally effective and equally easy to perform.