Although automated cell separators (apheresis) have undergone a lot of technical refinements, the effect of the procedure on hematological indices of donors is rarely taken into account. The purpose of this study is to identify potential hematologic changes in donors undergoing erythrocytapheresis. 30 apparently healthy adult donors were evaluated. Erythrocytapheresis procedure was performed using automated equipment. Hematologic measurements (hemoglobin, hematocrit, white blood cells counts and platelets) were analyzed before and after erythrocytapheresis in all donors. We observed a significant decrease in the donors in hemoglobin (p