Estimates of heat flux from direct measurements of vertical velocity-temperature fluctuation correlations have been obtained from vertical profiles through turbulent patches in the main thermocline. These have been compared to more indirect flux estimates derived from dissipation rates of turbulent kinetic energy and temperature variance. Because record lengths are limited by the thickness of observed turbulent patches, uncertainties are larger than would be expected from relatively longer horizontal records. The best estimate of dissipation flux coefficient from these data is about 0.15--0.2, but it is characterized by a large range of sample values. This implies mixing efficiencies (flux Richardson numbers) are about 0.13--017. This is within the range of laboratory estimates but is different from measurements in turbulent tidal fronts. ¿ American Geophysical Union 1996