The authors have occasionally noted Graves ophthalmopathy patients with stable, restrictive hypotropia who demonstrate excellent initial postoperative realignment, only to develop marked overcorrection within weeks to months after surgery. The charts of 12 consecutive patients who underwent a first operation for single, uncomplicated vertical muscle imbalance were evaluated. Five patients were identified who developed an overcorrection 2 to 5 months after surgery (overcorrected group). A stable comparison group of seven patients retained stable orthotropia after surgery. In cases of patients with late overcorrection, proptosis and superior rectus muscle volume, as measured preoperatively, were significantly greater than in the stable comparison group. There also was postoperative limitation of infraduction in most instances.