The upper ocean heat budget in the western equatorial Pacific warm pool is analyzed for a 3-month period from mid-September through mid-December 1992 using data from the Tropical Atmosphere Ocean (TAO) array enhanced for the Coupled Ocean Atmosphere Response Experiment. Surface heat and moisture fluxes were measured from a centrally located TAO current meter mooring at 0°, 156°E. Lateral heat advection was estimated using temperature data from moorings within 150–250 km of 0°, 156°E. Mixing was estimated as the residual of the heat balance and compared to estimates of mixing based on the Niiler-Kraus parameterization of entrainment mixing. The analysis shows that for the diurnal cycle and for daily to weekly timescale variations like those associated with westerly wind bursts, the sea surface temperature (SST) variability is to a large extent controlled by shortwave radiation and latent heat flux. However, three-dimensional processes can also be important. For example, in early October 1992, the SST at 0°, 156°E increased by nearly 1°C in 7 days due predominately to westward heat advection. Also, the dynamical response to a moderately strong wind burst in late October 1992 included a deepening of the pycnocline, which affected the rate of entrainment cooling, and a reversal of the surface current, which affected the zonal heat advection. The importance of three-dimensional processes (particularly heat advection) in the warm-pool heat balance during this 3-month study period is confirmed by comparing the observed temperature variability with that simulated by a one-dimensional mixed layer model.