The aim of this study was to investigate the effects of chronically administered aluminum on erythropoiesis in rats. After treatment (i.p. injections of Al(2)(SO(4))(3), 50 micromol/kg body weight, five times a week) for 3 months, the treated (Al) group showed significantly decreased hemoglobin concentration (32%) and hematocrit (24%) compared with the control group. Serum iron decreased significantly in the Al group, whereas total iron binding capacity did not change. Treatment did not alter the activity of hepatic, renal or cerebral delta-ALA-D. Biochemical measurements related to 2-thiobarbituric acid-reactive substance (TBARS) levels from serum and hepatic, renal and cerebral homogenates also did not change after treatment. Hepatic concentrations of aluminum were higher in the Al group than in the control group. Renal and cerebral aluminum concentrations did not vary between groups. The present results indicate that exposure to aluminum sulfate promotes signs of anemia in rats as a consequence of alterations in iron status.