Objective: To estimate the prevalence of polypharmacy, describe the pharmacotherapeutic classes used, and investigate whether polypharmacy is associated with demographic and socioeconomic indicators, regardless of the number of diseases, among participants in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) baseline (2008-2010). Method: In this analysis, 14,523 adults and elderly (35-74 years) participated. Polypharmacy was characterized as regular use of five or more medicines. The demographic and socioeconomic indicators analyzed were: gender, age, education level, per capita family income, and access to private health insurance. The independent association between demographic and economic indicators and polypharmacy was estimated by binary logistic regression. Results: The prevalence of polypharmacy was 11.7%. The most used drugs were those with action on the cardiovascular system. After adjustments, including by number of diseases, the chances of being on polypharmacy treatment were significantly higher among women, older participants and those with greatest number of diseases. Individuals without health insurance had lower chance to be under polypharmacy, as well as those with lower income. Conclusion: The occurrence of polypharmacy among ELSA-Brasil baseline participants was mainly due to drugs for the treatment of chronic diseases. The relation between polypharmacy and the female gender, as well as its association with old age, are in consonance with the results obtained in other studies. Despite the absence of an association between polypharmacy and education level, the income and health insurance results reinforce the existence of social inequalities regarding drug use.