The authors investigate the efficacy and safety of isolated superior oblique tucking in patients with congenital superior oblique palsy. The study includes 21 cases: eight females and 13 males aged 2-34 years. All had obvious superior oblique under action and ipsilateral inferior oblique over action. The hyper deviation in primary position ranged from 6-18 prism dioptres: mean 10.9±3.3 preoperatively. Postoperatively, the mean deviation was 1.5 prism dioptres ±2.6 (2-6). In the reading position, the mean hyper deviation preoperatively was 15.6 prism dioptres ±3.6 (12-22) reducing postoperatively to 2.6 prism dioptres ±3.1 (0-10). The amount of superior oblique tuck ranged from 5-12mm, mean 8.3±2.3. There was no correlation between the surgical amount and corrected vertical deviation in the primary position and reading position, or with the preoperative deviation. The average corrected objective extorsion was 9.5 degrees ±3.3 in 14 patients and also not related to the amount of superior oblique tucking. The abnormal head posture resolved or was less than five degrees in all patients postoperatively. Three patients had a small reversal of their hyper deviation in primary position postoperatively. No patient complained of vertical diplopia in the reading position. All 21 patients had a -1 to -1.5 scale of limitation in elevation in adduction – iatrogenic Brown’s syndrome – but all asymptomatic. The authors proposed that isolated superior oblique tuck could correct hyper deviation of 10 prism dioptres on average and 15 prism dioptres maximum in reading position with correction of objective extorsion by approximately 9.5 degrees on average. For this surgery they recommend that patients have vertical deviations less than 15 prism dioptres in primary position, obvious superior oblique under action (Knapp type 2), ocular extorsion and superior oblique tendon laxity proven by forced duction test. The latter test was considered essential for planning surgery.