Purpose: To analyze refractive change in children with congenital ptosis who have undergone unilateral levator resection. Methods: All charts of patients with congenital ptosis who underwent one levator resection performed by 2 pediatric ophthalmologists at the University of Minnesota from 1981 through 1995 were reviewed. Postoperative refractive changes were analyzed within the group of eyes that underwent ptosis repair and within the group of fellow eyes that served as age-matched controls. The preoperative and postoperative refractive error of each operated eye was also compared with its paired unoperated eye. Results: Complete preoperative and postoperative refractive data were available for 28 patients with congenital ptosis requiring only one levator resection. The mean age at surgery was 3 years 8 months. The preoperative mean ptosis was 3.5 mm (range, 1.5-6 mm). At the last postoperative visit (mean, 20 months; SD, 11 months), the mean refractive change in the operated eye was 1.23 D sphere (range, 0-3.50 D; P = .061) and 0.83 D cylinder (range, 0-3.00 D; P = .002). Within the group of control eyes, no significant mean spherical or cylindrical changes were found at the last postoperative visit. Fourteen eyes with preoperative ptosis had a cylindrical change of 0.75 D or more, compared with a similar change in 4 control eyes. When refractive errors were compared interocularly, no statistically significant differences were found. Conclusions: Our results showed significant cylindrical change in eyes that underwent levator resection for unilateral congenital ptosis. Careful refraction is necessary after unilateral levator resection.