Though never validated, the flashlight test is a commonly used screen for nocturnal hypoglycemia. Between 2 a.m. and 4 a.m., we applied the test to 107 children at Eagle's Nest Camp for Children with Diabetes. We validated the test against simultaneously determined capillary blood glucose values (Glucoscan). An eyelid squint in response to the flashlight was considered an intact test. No significant difference existed between mean glucoses for intact and nonintact responses. Both sensitivity and positive predictive value are too low for the flashlight test to be useful in screening for nocturnal hypoglycemia.