New paleontologic and radiometric data and a synthesis of redefined provincial biostratigraphic frameworks provide the basis for a new geologic time scale for the Cenozoic strata of Oregon and Washington. The new geologic time scale integrates provincial molluscan, foraminiferal, land-mammal, and megafloral biochronologies of the Pacific Northwest. The integrated biostratigraphic framework incorporates new data on planktonic microfossils from western Oregon and Washington and is correlated with the Cenozoic worldwide geologic time scale. The biostratigraphic correlations are augmented by integration of radiometric age data. The new provincial geologic time scale revises the 1944 chart on “Correlation of the Marine Cenozoic Formations of Western North America” and provides a basis for time-stratigraphic correlations within the context of the current worldwide geologic time scale.