OBJECTIVE To evaluate the effectiveness of very early surgery for establishing straight eyes and sensory fusion in patients with congenital esotropia. METHODS A review of consecutive patients with congenital esotropia who underwent surgery between 13 and 19 weeks of age. METHODS A children's hospital with a teaching affiliation. METHODS Seven patients who had surgery between 13 and 19 weeks of age. METHODS A bilateral medial rectus recession through a fornix incision with recessions ranging from 5.75 to 6.5 mm in infants younger than 6 months of age. METHODS Sensory fusion as measured by stereo acuity and Worth four-dot testing and motor alignment within 8 prism diopters. RESULTS Five of the seven patients achieved essentially straight eyes with tropias of less than 8 prism diopters after one horizontal surgery. Five patients cooperated with sensory testing, and all showed stereo acuities that ranged from 400 to 40 seconds of arc. Three children had evidence of high-grade stereo acuity by showing stereopsis on random dot stereograms (Randot, Stereo Optical Co, Chicago, Ill) and by fusing the Worth four-dot test at distance and near range. Two of the patients with high-grade stereo acuity achieved a stereo acuity of 40 seconds of arc by Titmus testing; however, one had a late reduction of stereo acuity to 70 seconds of arc. CONCLUSIONS Very early surgery can result in excellent motor alignment and high-grade stereo acuity in some patients with congenital esotropia.