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Arvicoline rodents are presently the most useful biostratigraphic tools in North America for the correlation of continental sediments that are Blancan in age or younger. Recent work in the Central Great Plains suggests that they also may have value for intercontinental correlations. About one-third of the Blancan genera of arvicolines became extinct at the end of Blancan time, while the earliest post-Blancan faunas contain very few arvicolines. The fauna from beneath the "type-S Pearlette Ash" at the type section of the Sappa Formation (1.2 million years B.P.) contains the earliest dated record of a Microtus-like microtine (Allophaiomys) from North America. Essentially the same arvicoline occurs beneath the Kansas Till in Doniphan County, Kansas. This arvicoline may well be an immigrant from Eurasia which entered North America in the Early /Pleistocene and may be of considerable use in correlation with the European sequence. A zonation for the Late Cenozoic in North America based on arvicolines is proposed, and evolution within the Ondatrini is discussed.