Internal ophthalmoplegia was found in eight eyes of four patients with juvenile-onset diabetes. All eight eyes had received argon laser panretinal photocoagulation (PRP) for proliferative diabetic retinopathy. Internal ophthalmoplegia was not found in any of the 14 eyes of seven patients with juvenile diabetes who had not had photocoagulation treatment. This group included one patient in whom internal ophthalmoplegia was present after treatment. Laser injury to the short ciliary nerves, as they course anteriorly on the inner surface of the sclera, is the probable cause of internal ophthalmoplegia in these patients. To my knowledge, this complication has not been reported previously, but it appears to be a common side effect of PRP.