To determine the genetic relationship of anadromous and resident life-history types within and among drainages, and compare several hatchery strains to their progenitor populations, brook charr Salvelinus fontinalis were examined for allozyme and mitochondrial DNA variation. Greater genetic similarity of sympatric anadromous and resident charr was found compared to similar life-history forms allopatrically, suggesting the two life-history types are not reproductively isolated. Low divergence among the mtDNA haplotypes suggests that the two life-history types are members of the same evolutionary lineage. Population differentiation from mtDNA data exceeded that from estimates based on allozymes. Genetic deviations from expectations suggest that the hatchery strains were derived from few individuals.