Mitochondrial sequence variation was examined in the northern snakehead, Channa argus (Cantor, 1842), a species of fish native to Asia and recently collected in the eastern United States. There are seven unique haplotypes in 29 specimens studied, with no haplotype shared between areas of introduction. One haplotype was shared by 15 individuals from the Potomac River system (both males and females <480 mm total length), indicating possible breeding within the system. A single large adult male from the Potomac River system has a unique haplotype. All Crofton, Maryland, specimens had one haplotype. Two haplotypes were found in Meadow Lake, FDR Park, Philadelphia, Pennsylvania. Unique haplotypes were found in Wheaton, Maryland, and Shrewsbury, Massachusetts. These results support the conclusion that there were several independent introductions of the northern snake-head into these waters, and that no two introductions came from the same maternal source.