The genomes of all extant cetaceans are characterized by the presence of the so-called common cetacean DNA satellite. In the mysticetes (whalebone whales) the repeat length of the satellite is 1,760 bp. In the odontocetes (toothed whales), other than the family Delphinidae, the repeat length is usually approximately 1,740 bp. The Delphinidae are characterized by a repeat length of approximately 1,580 bp. It has been shown in odontocetes that the satellite evolves in concert and that differences between species, with respect to the sequence of the satellite, correspond reasonably well to their evolutionary distances. In the present study the sequence of the satellite was determined in three repeats in each of seven mysticete species, and a consensus for each species established. Parsimony and neighbor-joining analyses based upon sequences of all repeats showed that the primary evolutionary distinction among the mysticetes is between the Balaenidae sensu stricto (i.e., the bowhead whale and the right whale) and all remaining species, including the pygmy right whale, a species that usually has been included in the Balaenidae. The comparisons also showed that the humpback whale and the gray whale were approximately equidistant from the blue whale and the fin whale (genus Balaenoptera). Concerted evolution of the satellite was also demonstrated among the mysticetes, but it appeared to evolve more slowly in the mysticetes than in the odontocetes.