The study examines a significant scientific and policy issue that alcohol and drug research has not adequately addressed: what are the effects of having a family member with alcohol or drug dependence (AODD)? What are the effects on health and psychosocial problems of family members and the additional health services they use, and what are the resulting costs to the health system? The original study compared enrollees in a large health plan who have a family member diagnosed with AODD to family members of individuals without an AODD and family members of individuals with other chronic conditions (diabetes and asthma), using large matched samples. We propose to examine whether findings from the original study of higher costs and more health conditions among family members of persons with AODD (and reduced family costs after the index AODD member receives successful AODD treatment) persist over time in order to better estimate the full cost of these families to health systems. We use the large, well-matched health plan cohorts from the original study, in which we analyzed data from 1 year before the date of the index family member's AODD diagnosis to 2 years after. We propose to examine 5 additional years of data, for a total study period of 8 years. We use innovative techniques with electronic medical record and other health plan data to examine medical conditions of family members and to estimate utilization changes due to treatment. To understand the long-term trends in utilization and costs of AODD family members and compare them to other demographically similar cohorts, we will use generalized linear models (for yearly comparison) and hierarchical linear models (for analysis of multi-year trends). We will examine the relationships of the index patient's dependence type, receiving AODD treatment, and co-occurring medical and psychiatric conditions to the utilization and costs of their family members, examining cost for children and adult family members separately. We will also compare AODD family members with family members of individuals without AODD, and with family members of patients with diabetes and asthma over the 8 years. Using the cohort of adolescents with AODD, we examine the health conditions and costs of their siblings and parents. Finally, through chart review and other health plan data, we determine if the child family members of AODD adults are less likely to receive optimal preventive care, or are more likely to have records indicating family, legal, or school problems than children in the comparison families. The study has high significance for critical issues such as placing interventions in primary care, screening for family problems in pediatrics, treating family members as part of AODD services, and for health policy (including AODD benefits in the list of high value health care services, with low cost-sharing). The study examines the medical conditions and health care utilization and costs of family members of adults and adolescents with alcohol or drug dependence (AODD) over 8 years, comparing them with family members of individuals without AODD and with family members of diabetes and asthma patients. It uses innovative IT methods and has significant clinical and policy implications for placing interventions in primary care, screening for family problems in pediatrics, and treating family members as part of AODD services.