This study assessed cumulative effects of multiple mild head injuries on cognitive functioning in children. Subjects included 1586 children with one mild head injury, 278 with two, and 51 with three or more head injuries between birth and age 10 years and controls without head injuries matched on gender and total number of injuries. The number of head injuries and injuries not to the head was associated with decreasing performance on measures of intelligence (p < .01), reading (p < .01), and math (p = .02). There was no interaction between case-control status and number of injuries, indicating a similar relationship between cognitive outcomes and number of injuries in head-injured cases and controls. After adjustment for covariates, the relationship between number of injuries and cognitive outcomes became nonsignificant. This study suggests that cognitive deficits associated with multiple mild head injury are due to social and personal factors related to multiple injuries and not to specific damage to the head.