The ProHeat(trade mark) reusable hot pack is being used increasingly as a substitute for the standard hydrocollator steam pack. This study evaluated the effects of these two modalities on skin temperature. Seventeen subjects were studied during separate 30-minute applications of a ProHeat pack with a wet barrier, a ProHeat pack with a dry barrier, a hydrocollator pack, and a control pack on their nondominant calf. We measured the skin interface temperature and pack surface temperature during each application with surface thermocouples. The skin interface temperature rise time to the minimum therapeutic temperature (104 degrees F) and the total time at and above the minimum therapeutic temperature, for each application, were analyzed using an analysis of variance (ANOVA) with repeated measures (p<.05). The ProHeat pack application, with one layer of wet toweling as a barrier, was not significantly different from the hydrocollator steam pack application. We conclude that the ProHeat pack, prepared with a wet barrier, can be considered a viable alternative to the standard hydrocollator steam pack.