The distribution of the four founding lineage haplogroups in Native Americans from North, Central, and South America shows a north to south increase in the frequency of lineage B and a North to South decrease in the frequency of lineage A. All four founding lineage haplogroups were detected in North, Central, and South America, and in Greenberg et al.'s ( Curr. Anthropol. 27:477–497) three major linguistic groups (Amerind, NaDene, and Eskaleut), with all four haplogroups often found within a single population. Lineage A was the most common lineage in North America, regardless of language group. This overall distribution is most parsimonious with a single wave of migration into the New World which included multiple variants of all four founding lineage types. Torroni et al.'s ([1993a] Am. J. Hum. Genet. 53:563–590) report that lineage B has a more recent divergence time than theother three lineages can best be explained by multiple variants of lineagesA, C, and D, and fewer variants of lineage B entering the New World. Alternatively, there could have been multiple waves of migration from a single parent population in Asia/Siberia which repeatedly reintroduced the same lineages to the New World. © 1995 Wiley-Liss, Inc.