Poverty rates in high-poverty and low-poverty rural counties, and, thus, the spatial concentration of poverty, are affected by poverty-specific differences in in-migration and out-migration patterns. These patterns are investigated using 1985–90 county-to-county migration data from the decennial census. Effects on poverty rates of four migration flows (in- and out-migration of poor, in- and out-migration of nonpoor) are quantified, and their impacts on spatial concentration of poverty are assessed. The effect of selected county characteristics on the migration of the poor and nonpoor in nonmetro counties are estimated. The poor are as mobile as the nonpoor, and the migration patterns of both poor and nonpoor generally maintain and reinforce the pre-existing spatial concentration of poverty.