Previous phylogenetic studies using mitochondrial DNA sequences of the brown bear Ursus arctos have separately defined two major lineages in Europe, three in Alaska, and three in Hokkaido Island of Japan. To reconstruct phylogenetic relationships among worldwide populations of the species, nucleotide sequences of the mitochondrial DNA control region and cytochrome b were determined for some additional subpopulations of Asia (Gobi and Tibetan), and then all the data including previously reported sequences were compared. The resultant phylogenetic trees showed that the worldwide populations could be grouped into at least five lineages. One of the five lineages had a wide distributional range covering Eurasia, Alaska, and central Hokkaido. Moreover, it is likely that populations from eastern Hokkaido and eastern Alaska are the direct derivatives of a single lineage. These results suggest that brown bears may have widely colonized Eurasia and North America from their original areas somewhere in Eurasia more than once.