Epilepsy has a significant impact on a child's life, the extent to which is based on four factors: epilepsy, cognition, behavioral, and physical/neurologic function. This study evaluates the ability of the 44-item Impact of Childhood Neurologic Disability Scale (ICND) to assess each of these four realms. Parents of children (aged 2 to 18 years) with epilepsy rated their child's overall quality of life and completed the ICND. External validation compared the ICND with (1) neurologists' reports of children's behavior, cognitive abilities, physical/neurologic disability, and epilepsy; and (2) parents, teachers, and children's ratings on six 'criterion standard' questionnaires. Families of 68 children with epilepsy only and 29 children with 'epilepsy-plus' (additional cognitive, behavioral, or physical/neurologic disability; 39 males, 58 females; mean age at testing 10 years 3 months [SD 4.5] age range 2 to 17 years) participated. Internal consistency was excellent (Cronbach's alpha=0.92) as was test-retest reliability (intraclass correlation=0.89). Caregivers distinguished the impact of each of the four realms. Scores were negatively related to quality of life (Pearson's r=-0.59). Children with high ICND scores had more difficulties at home and school. Their parents saw them as less rewarding and adaptable and the children saw themselves as less intelligent and less popular with more emotional problems. In addition, children with 'epilepsy-plus' had significantly higher total ICND scores as well as markedly elevated scores within each of the four realms when compared with the epilepsy-only group. It is concluded that the ICND is an accurate, quick measurement tool reflecting the impact of behavior, cognitive learning ability, physical/neurologic disability, and epilepsy on children and their families.