This volume covers Leg 86 of the cruises of the Drilling Vessel Glomar Challenger. One of the long-standing goals of the Deep Sea Drilling Project (DSDP) has been to study the oceanic paleoenvironment of the western Pacific through deep sea drilling. Two complementary legs were planned to address this problem: Leg 86 in the western North Pacific and Leg 90 along the Lord Howe Rise in the western South Pacific. The primary objective of Leg 86 was to drill a north-south transect of four sites across the Kuroshio Current system, from subtropical to subarctic waters. The late Neogene sections recovered at these sites would help to unravel the preglacial and Quaternary paleoceanographic history of the Kuroshio Current system and to determine whether the Miocene onset of biosiliceous sedimentation in the region was synchronous or diachronous. Hydraulic piston coring (HPC) of two holes at each site was planned to allow a high-resolution late Neogene midlatitude stratigraphy using paleomagnetics, tephrachronology, stable isotopes (when possible), and biostratigraphy. Secondary objectives of Leg 86 included the following: First, to hydraulic piston core the Cretaceous/Tertiary boundary at the Shatsky Rise for midlatitude calcareous biostratigraphic, paleomagnetic, and geochemical studies. Second, to recover a "type" North Pacific red clay section for geochemical, paleomagnetic, and geotechnical studies. Third, to determine the thickness and character of sediments at the site of the proposed Defense Advanced Research Projects Agency (DARPA) downhole seismometer experiment (Leg 88) to allow design of casing strings. Eleven holes at six sites, Sites 576 through 581, were occupied during Leg 86 as the Glomar Challenger sailed from Honolulu, Hawaii to Yokohama, Japan. Leg 86 took place between May and June of 1982.