All published and unpublished population frequency data that could be located for U.S. populations are tabulated and presented for the serum group systems haptoglobin (alpha-chain), group specific component, and transferrin and for the common beta-chain variants of hemoglobin. Results obtained by combining data for comparable racial/ethnic groups are also presented. Some evidence is presented to indicate that the results obtained from the combined data may give better information on frequencies for the U.S. population at large than is obtainable from studies conducted in restricted geographic areas.