A new Mesozoic isochron chart of the northwestern Pacific Ocean has been completed by utilizing all the currently available data from 357 cruises. Our chart provides the first whole view of the Mesozoic magnetic anomaly lineations in the northwestern Pacific Ocean and yields essential information for understanding the problems of the Mesozoic magnetostratigraphic time scale and the evolutional history of the Pacific plate. The Mesozoic magnetostratigraphic time scale must be recalibrated using not only the Hawaiian lineation set but also other Mesozoic lineation sets. The lack of lineation M0 in the lineation sets other than the Hawaiian lineation set indicates that a reorganization of the ridges except the Pacific-Farallon ridge occurred between chrons M1 and M0 (nearby 120 Ma). The eruption rate of the Shatsky hotspot seems to be comparable to that of the Reunion hotspot at their initial stage. The growth of the Pacific plate began in a small triangular region at about 190 Ma. ¿ American Geophysical Union 1992