Radiolarian responses to the 1982-83 California El Nino event were unusually high standing crops of both warm and cold water radiolarians, high diversity, and the appearance of distinctly central gyre and eastern tropical Pacific faunas. These and other observations suggest that anomalously strong transport from the west and south occurred through at least November 1953 and that the California Current had shifted eastward over the Southern California Eorderland. A generic group of radiolarians, the spongasterids, was used effectively in monitoring these water mass influences. Radiolarian distributions in 3.-3.5 Ma circuoi-northeastern Pacific sediments indicate a warm North Facific at this time. Marked breaks in distributional trends off southern Baja California suggest an oceanic frontal zone in this area, To the south radiolarian assemblages exhibit a distinctly eastern tropical Pacific character. Spongaster pentas occurs as far north as Deep Sea Prilling Site 173. This suggests periodic breakdowns of this frontal zone (El Ninos?) may have occurred.