AIMS: This study investigates ethnic and socioeconomic risk factors for hospital admissions related to illicit drug abuse in second-generation immigrants in Sweden. METHOD: Cox analyses of proportional hazards were used to estimate the relative risk of sociodemographic covariates in analyses of register data on hospital admissions because of illicit drug abuse during 1990-99. The study population was a national cohort of 1.25 million residents (aged 10-30 years). RESULTS: Second-generation immigrants had two- to three fold higher age and sex-adjusted relative risks (RRs) for hospital admissions because of illicit drug use compared with the Swedish majority population with a limited variation between different ethnic groups. The RRs decreased greatly after the model was adjusted for socioeconomic indicators of the childhood household. Inter-country adoptees had the highest risk for hospital admission related to illicit drug abuse of all study groups after adjustment for sociodemographic variables (RR 2.8). CONCLUSIONS: Second-generation immigrants are at particular risk for illicit drug abuse in Sweden. Adverse socioeconomic living conditions are very important in explaining this high risk.