Abstract Migration alters both the origin and destination of migrants in a variety of ways. This study uses data recently made available by the Internal Revenue Service to document gains and losses of both persons and income accruing to counties in the United States as a result of internal migration between 1992 and 1993. The degree to which migration alters the size of a county's population as well as the amount of income received in that county is assessed by means of effectiveness rates which are ratios of net flows to total flows. The majority of counties, especially those in the South and West gained both migrants and income during the period; losses were confined largely to the Northeast, Great Plains and California. Counties at the edges of large metropolitan areas gained income even more rapidly than people; counties containing large central cities lost income even faster than they lost migrants. Amenity-laden recreational and retirement counties were also among those who gained both people and income via migration. Overall, these results indicate an exacerbation of demographic and economic differences between regions as well as within metropolitan areas.