SUMMARYObjective: To estimate long-term socioeconomic consequences and health care costs of epilepsy with onset in childhood and adolescence. Methods: A historical prospective cohort study of Danish individuals with epilepsy, age up to 20 years at time of diagnosis between January 1981 and December 2012. Information about marital status, parenthood, educational level, employment status, income, use of the health care system, and cost of medicine was obtained from nationwide administrative and health registers. Results: We identified 12,756 and 28,319 people with diagnosed with epilepsy, ages 0-5 and 6-20 years at onset, respectively. Using follow-up data for a maximum of 30 years, 1,394 of those ages 0-5 years at onset were compared with 2,897 controls persons without epilepsy, and 10,195 of those ages 6-20 years at onset were compared with 20,678 controls without epilepsy. Compared with people without the epilepsy, those with epilepsy tended to have a lower level of education, to be less likely to be married, to be more likely to live alone, and to have higher divorce and unemployment rates, lower employment rates, and people with epilepsy were more likely to receive disability pension and social security. Income was lower from employment, which in part was compensated by social security, sick pay, disability pension and unemployment benefit, sick pay (publicfunded), disability pension, and other public transfers. Predicted health care costs 30 years after epilepsy onset were significantly higher among persons with epilepsy onset at 0-5 and 6-20 years, including costs for outpatient and inpatient services (hospital services), emergency room use, primary health care sector (general practice), and use of medication. Significance: The long-term negative effects on all aspects of health care and social domains, including marital status, parental socioeconomic status, educational level, employment status, and use of welfare benefits compared with controls without epilepsy calls for increased awareness on childhood-and adolescentonset epilepsy.