A cross-sectional study of children living in poor areas in the city of Salvador, Bahia State, Brazil, was carried out in 2006 to investigate the prevalence of use of prescribed and non-prescribed medication. This population-based study included 1,382 children aged 4-11 years. The use prescribed and non-prescribed medication during the 15 day period preceding the interview was adopted as the dependent variable. Of the 1,382 children, 663 (48%) had used at least one type of medication in the 15 days prior to the interview: in 267 cases (40.3%), mothers reported that the child had taken prescribed medication, while in 396 cases (59.7%), the child had taken medication that had not been prescribed by a physician. The most commonly prescribed drugs were analgesics (42.3%), systemic antibiotics (21.3%) and antiasthmatic (16.5%). With respect to non-prescribed drugs, the most common were analgesics (65.2%), antitussives (15.7%) and vitamins (9.3%). The results show a high prevalence of the use of non-prescription drugs among poor children, and large drug purchases of drugs by the head of household, highlighting deficiencies in coverage of the health system.