Anterior segment ischemia (ASI) is a potentially blinding complication of extensive eye muscle surgery. Eyes have been described with this complication following surgery on as few as two rectus muscles, especially in patients with thyroid dysfunction or other medical illnesses. In an attempt to assess the risk of ASI, we have reviewed the records of 34 eyes in 26 patients who underwent surgery on three or four rectus muscles. Seven eyes of six patients with thyroid ophthalmopathy which underwent two-or three-muscle surgery were also studied. Evidence of clinically significant ASI was apparent in only one patient during a follow-up period of seven months to eleven years. This case was mild and no visual loss resulted. Our findings suggest that surgery on three or four rectus muscles in healthy patients is probably safe when performed in a staged fashion.