The relationship between linguistic differentiation and evolutionary affinities was evaluated in three tribes of the Pacific Northwest. Two tribes (Nuu-Chah-Nulth and Bella Coola) speak Amerind languages, while the language of the third (Haida) belongs to a different linguistic phylum--Na-Dene. Construction of a molecular phylogeny gave no evidence of clustering by linguistic affiliation, suggesting a relatively recent ancestry of these linguistically divergent populations. When the evolutionary affinities of the tribes were evaluated in terms of mitochondrial sequence diversity, the Na-Dene-speaking Haida had a reduced amount of diversity compared to the two Amerind tribes and thus appear to be a biologically younger population. Further, since the sequence diversity between the two Amerind-speaking tribes is comparable to the diversity between the Amerind tribes and the Na-Dene Haida, the evolutionary divergence within the Amerind linguistic phylum may be as great as the evolutionary divergence between the Amerind and Na-Dene phyla. Hence, in the New World, rates of linguistic differentiation appear to be markedly faster than rates of biological differentiation, with little congruence between linguistic hierarchy and the pattern of evolutionary relationships.