To evaluate the risk of iron deficiency and anemia connected with the use of modern copper intrauterine devices, serum ferritin, transferrin, iron, hemoglobin and hematocrit levels, red cell counts, and morphology, as well as red cell indexes were determined in 40 women and in 19 controls. Follow-up was for one year. Mean hemoglobin, hematocrit, serum iron, and serum ferritin levels decreased and serum transferrin levels increased significantly in the study population. About 20% of intrauterine device users but none of the controls showed signs of iron deficiency, and 10% had clinical anemia at 12 months of use. No differences were found between the three different copper intrauterine devices tested (Nova T, Multiload and Fincoid). Because the risk of anemia did not correlate with subjective evaluation of the amount of bleeding, it is recommended that hemoglobin levels should be determined for all intrauterine device users before its insertion and at six and 12 months of use. In those with decreased hemoglobin levels, serum ferritin should be measured and iron replacement instituted or the device removed.