Inferior oblique myectomies or Z-myotomies were performed on 159 eyes of 121 patients who had an overacting inferior oblique muscle or muscles. The results were as follows; 1. Success rates were 95.5% in myectomy and 71.4% in Z-myotorny. 2. Recurrence rates were 2.7% in myectomy and 14.3% in Z-myotomy. 3. There were no other complications to include the adherence syndrome.