The liquid feed boundary layer has recently received large attention due to its mass transfer resistance in the pervaporation process. The boundary layer also, however, causes a heat transfer resistance. A theory on both the heat consumed in pervaporation and the heat transfer in pervaporation is used to experimentally evaluate the heat consumption, as well as the heat transfer resistance in the liquid feed boundary layer. In determining the heat consumed in pervaporation, it was observed that it could best be described as the sum of the heat of vaporization and the heat of expansion. It was also observed that the heat transfer in the liquid boundary layer is, in some cases, rate determining for the pervaporation process, a phenomenon which is termed temperature polarization.