Leg 167 will investigate the evolution of oceanogaphic conditions in the north Pacific Ocean and will document changes in flow of the California Current system and associated changes in coastal upwelling. These data will be used to reconstruct north Pacific climate conditions through the Neogene, concentrating upon the time period since the advent of northern hemisphere glaciation, approximately 2.5 Ma to the present. Approximately one third of the proposed drill sites will also sample lower and middle Miocene sediments to reconstruct a Neogene history of the California Current. The results of Leg 167 drilling will also be used to better understand the links between climates of the north Pacific Ocean and western North America, particularly in terms of temperature change and changes in precipitation. Thirteen proposed sites and five alternates are organized into three transects across the California Current (Baja Transect, approximately 30 degrees N; Conception Transect, approximately 35 degrees N; and Gorda Transect, approximately 40 degrees N) and one coastal transect extending from northern Baja California to the California/Oregon border, 30 degrees N to 42 degrees N. Each of the three transects across the California Current will compare deep-water sites near the core of the California Current to coastal upwelling sites near shore. The coastal transect will examine variations in upwelling and productivity along the California margin, and will also examine intermediate water properties in many of the basins of the California Continental Borderland.