This paper discusses the design and test of a pressure controlled heat pipe (PCHP) for spacecraft thermal management. The PCHP combines a conventional grooved aluminum-anmionia heat pipe with a variable-volume noncondensable gas reservoir to create a heat pipe whose conductance can be precisely controlled. Testing showed that a prototype PCHP was capable of maintaining a stable evaporator temperature within O.IK despite wide swings in heat load and heat sink temperature. A similarly-sized variable-conductance heat pipe (VCHP) yielded temperature swings of over 3.5 K for the same variation of heat load and sink temperature. Using a non-optimized control system, the PCHP was capable of maintaining evaporator temperature within 0.05K over time. The PCHP had a much faster transient response than other devices such as heated-reservoir VCHPs, as well as providing a means for changing the set point temperature after assembly. The PCHP is a significant advance over other means of temperature control, even in its current non-optimized state.