Pacific subtropical-tropical thermocline water exchange is estimated using the National Centers for Environmental Prediction oceanic general circulation model in which observed temperatures are assimilated. In the main thermocline (23<σt<26.2), the equatorward exchange transports are about 17 Sv (1 Sv = 106 m3 s−1) and 26 Sv at 10°N and 10°S, respectively. Consistent with observations and other model simulations, the water exchange has a Low-Latitude Western Boundary Current (LLWBC) pathway and an interior pathway. The equatorward LLWBC and interior transports are about 14 and 3 Sv, respectively, at 10°N and are about 15 and 11 Sv, respectively, at 10°S. The time required for subtropical water to penetrate into the equatorial ocean is usually less than 10 years. Exchange windows are also identified in both the North and South Pacific.