Expressions are obtained to describe the performance of a heat pipe in a regime of wet vapor flow. The analytical results are experimentally confirmed.A heat pipe, being a complex evaporative--condensative heat-transfer system, is characterized by high thermodynamic efficiency within a relatively narrow range of heat flux and temperature. This is because of several limitations on heat transfer connected with the hydrodynamics of the condensate and vapor flows, the evaporation kinetics, etc. [i]. Theoretical models which allow for these limitations make it possible to predict the performance of heat pipes with a certain error [2]. Nevertheless, some experimental studies [3,4] do not agree satisfactorily with the theoretical models.