Objectives: To explore the factors determining self-medication among the Spanish adult population, paying special attention to differences in pharmaceutical consumption patterns between the immigrant and autochthonous populations in Spain. Methods: Logistic regression models were used to evaluate the effect of several demographic, socioeconomic, lifestyle, and health-related variables on self-medication. Data were drawn from the adult sample of the 2006 Spanish National Health Survey, which included 29,478 individuals over 15 years old. Results: The results show that individuals at higher risk of self-medication were young, with a positive perception of health and no chronic diseases, frequent consumers of alcohol, widowers, holders of a private medical insurance policy not contracted through the civil servants' mutual funds, residents in the Autonomous Communities of Madrid or Valencia, and individuals born in central or eastern Europe. Conclusions: Identifying the profile of self-medicated drug users in Spain may help health authorities to target high risk individuals in order to comply with European Union public health goals. (C) 2009 SESPAS. Published by Elsevier Espana, S.L. All rights reserved.