Mitochondrial DNA from representative animals of 13 different cattle breeds was assayed for restriction fragment length polymorphisms (RFLP) to determine phylogenetic relationships and levels of variation among breeds; 16 different mitotypes were found, described by 20 polymorphisms. Within these 16 mitotypes two major lineages were apparent: an Afro-European and an Asian type. These were found to differ at over 2.3% of sites surveyed. None of the mitotypes found in the Asian lineage was detectable in the Afro-European lineage and vice versa. Within each of the major mitotypes there were no further significant differences within or among breeds. Using rates of mitochondrial evolution estimated from other species, the two lineages were estimated to have diverged between 575,000 and 1,150,000 years ago; well outside the 10,000 years bp timeframe postulated by a single domestication hypothesis. The results presented are concordant with those generated in other studies and provide strong evidence for an independent domestication of Asian Bos indicus. Furthermore, the grouping of all African indicine populations within the clade containing all Bos taurus lineages points to the hybrid origins of the humped cattle of that continent.