BACKGROUND: When and how to operate an early-onset esotropia (onset before 6 months of age) is still controversial. We conducted a retrospective study of such patients operated before the age of 24 months. PATIENTS AND METHODS: 82 patients were operated by one surgeon (GK) and followed by the same team. At 5 years post-operation, evaluation criteria included the residual angle of deviation, visual acuity (Birkhäuser Nr 505, 5 m) and binocularity (Lang stereotest I, Bagolini glasses). RESULTS: At 5 years, the residual angle was excellent (0 degrees to + 5 degrees ) in 67 % good, (>+5 degrees to +10 degrees or 0 to -5 degrees ) in 23 %, and poor (>+10 degrees or <-5 degrees ) in 10 %. During the 5 years of follow-up the rate of reoperation was 9.7 %. Isoacuity was obtained in 62 %, slight amblyopia (2 lines of interocular difference) was present in 32 %, and average amblyopia (> 3 lines of interocular difference) was noted in 6 %. Simultaneous perception was present in 53 %, whereas one eye was suppressed or results were undetermined in 47 %. No patient demonstrated stereoscopy using the Lang's stereotest I. CONCLUSION: The results from our study demonstrate that early surgery of early-onset esotropia has a favourable outcome on both visual acuity and the residual angle of strabismus. Simultaneous perception was achieved in 53 %. These figures are comparable to the results of the ELISSS multicentric study.