PURPOSE To report a systematic approach to, and the visual and electrophysiological effect of, eye muscle surgery in 100 patients with infantile nyustagmus syndrome (INS). METHODS Prospective, interventional case cohort analysis of clinical and eye movement data in 100 patients with INS who had virgin extraocular eye muscles operated on for nystagmus with or without combinations of strabismus and an anomalous head posture. All patients were followed at least 9 months after surgery. Outcome measures, part of an IRB approved study, included binocular visual acuity, head position, strabismic deviation, and eye movement recordings, from which waveform types and an Automated Nystagmus Acuityn Function (ANAF) was calculated. Computerized parametric and non-parametric statistical analysis of data were performed using standard software on both individual and group data. RESULTS There were 9 consistent surgical procedures used with the most common being that for a horizontal head posture alone (22%). Age at surgery averaged 14 years with 11 months followup. Sixty-eight percent had associated eye disease (optic nerve, retinal, amblyopia, cataracts). Group means in binocular acuity, strabismic deviation, head posture, abd ANAF measures from eye improved for all procedures. There were 12 (12%) reoperations without any serious surgical complications. Individual analysis revealed only age and head posture differences in outcome measures between the 9 procedures. CONCLUSIONS Using this approach, surgery on the extraocular muscles in patients with INS results in improvements in multiple aspects of ocular motor and visual function.