Seventy-six American mink (Mustela vison) from 8 localities were genotyped using 4 polymorphic microsatellite loci. This study was designed to test the hypothesis that genetic structure was partitioned within streams due to the close association of mink with riparian habitats. Six of the localities were streams in Lonoke County in central Arkansas, one was in Independence County, 143 km from Lonoke County, Arkansas, and one was in Tipton County, Tennessee (204 km away from the populations in Lonoke County). F_ST values indicated that the Tipton County site was genetically distinct from those from Arkansas. However, most F_ST values among the 7 localities in Arkansas (6 in Lonoke County and one in Independence County) indicated little genetic difference among these sites. There was no statistically significant relationship between genetic and geographic distances. The straight-line distance between sites was positively correlated with genetic distances based on F_ST, while riverine distances were negatively correlated with genetic distances, indicating that straight-line distance was a better predictor of genetic structure in mink, perhaps due to overland movements among streams. Genetic structure was not partitioned within streams because there was substantial gene flow among streams.