We compared hemoglobin electrophoresis patterns from infant blood samples collected in heparinized capillary tubes and on filter paper. This comparison was performed because hemoglobin electrophoresis of dried blood samples collected on filter paper has been advocated as a practical, reliable, and inexpensive method for mass screening programs, although the limitations of this technique have not been explored fully. We also summarize data from the North Carolina Newborn Hemoglobinopathy Screening Program, which relates to the advantages and limitations of hemoglobin electrophoresis from filter paper blood specimens.