The phylogenetic systematics of esocoid fishes are examined using comparisons of partial DNA sequences of the mitochondrial genes coding for the transmembrane protein cytochrome b and the 16S RNA ribosomal subunit. Nucleotide sequences from all species of umbrids, three species of esocids, and salmonid, osmerid, cypriniform, and neoteleostean outgroups were compared to determine patterns of molecular evolution and uncover evidence of phylogenetic relationships. Multiple sequence alignments for each of the two DNA regions examined were used to characterize the amount and type of change shown by the data. The sequences were analyzed under different models of molecular evolution using maximum-parsimony and maximum-likelihood optimality criteria of phylogenetic reconstruction. The phylogenetic analyses revealed previously undiscovered affinities between species of umbrids and esocids that imply the paraphyly of the Umbridae as currently defined. The following set of esocoid interrelationships is proposed: (((Esox, Novumbra), Dallia), Umbra). Esocoid classification is revised based on present findings.