Loop Heat Pipes have been shown to be reliable, self-starting, high capacity heat transport devices which offer significant performance improvements over conventional heat pipes. They are also capable of both constant and variable conductance operation, providing both temperature control and heat transport functions.Two different Loop Heat Pipes were tested to characterize their temperature control capabilities. Operation in both a passive, autoregulating mode and an active control mode were investigated. The test results demonstrate that temperature regulation in each mode is attainable. The effects of the operational environment on temperature control characteristics were found to be important and are discussed.