This study is the first large‐scale epidemiological investigation of acquired aplastic anemia (AAA) in South America. The objective was to estimate the incidence and to identify risk factors for AAA in Brazil. A national case–control study was conducted to investigate the risk factors for the disease. One hundred twenty‐five cases and 129 controls were included. Multiple logistic regression was used in the estimation of odds ratios (OR) to control confounding. The size of Brazil made it unfeasible to estimate the incidence of AAA in the whole country, and we limited the calculation to the state of Parana. The annual incidence of AAA in Parana was 2.4 cases/106 inhabitants. There was no positive association between chloramphenicol use and AAA (OR 0.4; 95% CI: 0.1–2.9). The OR of AAA associated with household pesticides that include organophosphates in their composition was 2.7 (1.0–8.4). The OR for the usage of unspecified thinner and/or acetone for at least 7 days was 3.0 (1.2–7.3). Cases of AAA in Brazil seem to be associated with some factors traditionally related to this disease, such as certain solvents and the incidence is similar to what has been reported from Europe. Am. J. Hematol. 71:268–274, 2002. © 2002 Wiley‐Liss, Inc.