ABSTRACT. Objective. To investigate whether family type and psychosocial risks indexed by family type were systematically associated with differences in health outcomes in children.Design and Subjects. The study is based on a longitudinal, prospective study of a large (n ؍ ϳ10 000) community sample of families, the Avon Longitudinal Study of Pregnancy and Childhood.Main Outcome Measures. Frequency of accidents, illnesses, and medical interventions.Results. At 2 years of age, children in single-parent and stepfamilies were disproportionately likely to experience accidents and receive medical treatment for physical illnesses. In addition, children in single-parent families and stepfamilies were more likely to be hospitalized or receive attention from a hospital doctor for an injury or illness. Exposure to psychosocial risks also were elevated in single-parent families and stepfamilies, compared with intact or nonstepfamilies, and these factors primarily accounted for the connection between family type and children's physical health.Conclusions. The consequences of family transitions on children's health extend beyond traditional mental health and behavioral outcomes and include accident proneness, illness, and receipt of medical attention. The mediating processes are not entirely attributable to social class differences connected to family type and may instead be associated with a range of psychosocial risks that are more frequently found in single-parent families and stepfamilies, compared with intact or nonstepfamilies. Prevention and intervention efforts directed toward children at risk for poor behavioral and mental health adjustment secondary to family disruption should consider children's physical health and health-related behaviors. Pediatrics 2000;106(5). URL: http://www. pediatrics.org/cgi/content/full/106/5/e68; family type, childhood, accidents, injuries, illnesses.ABBREVIATIONS. ALSPAC, Avon Longitudinal Study of Pregnancy and Childhood; OR, odds ratio. M embership in a single-parent family or stepfamily is associated with increased levels of significant behavioral, emotional, and academic problems in children. 1,2 The mechanisms underlying this connection are likely to involve, among other factors, financial adversity, increased stress directly related to family transitions, and increased exposure to additional psychosocial risks. 3,4 Compared with the extensive research base connecting family type (ie, membership in a 2-parent biological family, stepfamily, or single-parent family) and children's psychological adjustment, little is known about the physical health consequences of membership in diverse family types. One study 5 found that children in both single-parent families and stepfamilies were more likely to experience hospitalization or an injury attributable to accident than were children living with both biological parents. A smaller study found that children in single-parent families visited the general practitioner more and experienced more psychosomatic health problems. 6 A further study ...