The World Ocean Isopycnal-Level Velocity (WOIL-V) climatology was derived from the United States Navy's Generalised Digital Environmental Model (GDEM) temperature and salinity profiles, using the P-Vector Method. The absolute velocity data have the same horizontal resolution and temporal variation (annual, monthly) as GDEM (T, S) fields. These data have an horizontal resolution of 0.5 degrees ×0.5 degrees, and 222 isopycnal-levels (sigma theta levels) from sigma theta = 22.200 to 27.725 (kg m-3) with the increment delta sigma theta = 0.025 (kg m-3), however in the equatorial zone (5 degrees S – 5 degrees N) they are questionable due to the geostrophic balance being the theoretical base for the P-vector inverse method. The GDEM model, which served as the base for the calculations includes data from 1920s onwards and the WOIL-V will be updated with the same frequency as the GDEM. The climatological velocity field on isopycnal surface is dynamically compatible to the GDEM (T, S) fields and provides background ocean currents for oceanographic and climatic studies, especially in ocean isopycnal modeling. The climatology was prepared by the Department of Oceanography, Naval Postgraduate School.