The impact on their families of chronic illness in young Lebanese children and the relationship between such impact and perceived temperament of the child were assessed. The effect was greater in families of children with leukemia than in families of children with congenital heart defects. Chronically ill children were rated as more persistent/unstoppable, difficult, and irregular, and as less adaptable than were healthy children. Culturally determined perceptions of child temperament were examined with regard to differential impact of illness on the family.