To investigate the processes that maintain the large-scale, annual-average thermal structure of the equatorial Pacific, the three-dimensional ocean circulation for a large area is determined from a diagnostic model applied to repeated, meridional hydrographic sections along 150°W and 11O°W from 5°N to 5°S. Geostrophic balances are used to determine velocity profiles from 0 to 500 db across the boundaries of the region: zonal velocities across 150°W and 110°W at approximately 1° -lattitude intervals from 5°N to 5°S and meridional velocities across 5°N and 5°S averaged over the zonal distance between 150°W and 110°W. Poleward wind-driven flows across 5°N and 5°S based on climatological zonal wind stress are added to the geostrophic velocities in the mixed layers. To achieve overall mass conservation, the reference dynamic height field at 500 db is adjusted at four of the 21 stations by about 1 dyn cm. Horizontal nondivergence is used to determine meridional velocities between 0.75° and 5° latitudes... Abstract To investigate the processes that maintain the large-scale, annual-average thermal structure of the equatorial Pacific, the three-dimensional ocean circulation for a large area is determined from a diagnostic model applied to repeated, meridional hydrographic sections along 150°W and 11O°W from 5°N to 5°S. Geostrophic balances are used to determine velocity profiles from 0 to 500 db across the boundaries of the region: zonal velocities across 150°W and 110°W at approximately 1° -lattitude intervals from 5°N to 5°S and meridional velocities across 5°N and 5°S averaged over the zonal distance between 150°W and 110°W. Poleward wind-driven flows across 5°N and 5°S based on climatological zonal wind stress are added to the geostrophic velocities in the mixed layers. To achieve overall mass conservation, the reference dynamic height field at 500 db is adjusted at four of the 21 stations by about 1 dyn cm. Horizontal nondivergence is used to determine meridional velocities between 0.75° and 5° latitudes...