A late early Pliocene through Quaternary planktonic foraminiferal zonation has been established for the California margin based on a north-south transect of six drilled sequences (ODP Leg 167) from 31°N to 41°N. A total of eight zones are recognized for the last ~3.5 m.y., most of which are broadly applicable in the region, thus providing a biostratigraphic zonation of the sequence at ~0.5-m.y. intervals. The zonation is largely defined by changes in the Neogloboquadrina complex, which underwent a dynamic evolution within the California Current system during the late Neogene. The evolution and biogeographic changes in planktonic foraminiferal assemblages that are used to define the zonation occur over a large north-south sector of the California Current system. Although elements of the faunal changes are in part also observed in the north central and northwest Pacific regions, the evolutionary succession of changes described as a whole are probably unique to the California Current system. The diversity of the assemblages during the late Neogene appear to have remained relatively constant despite large-scale paleoclimatic change. The assemblages are consistently dominated by few taxa that almost always include the neogloboquadrinids and Globigerina bulloides. Low diversity and high dominance of the assemblages favored these and other taxa well adapted to upwelling systems exhibiting high seasonal surface-ocean variability. Apparently the oceanographic conditions that favor such assemblages have persisted at least for the duration of the late Neogene (3.5 Ma to present day).