A loop heat pipe (LHP) was flight tested as a Hitchhiker experiment on board the space shuttle Columbia. The STS-87 mission lasted from November 19 to December 5, 1997. A total of 213 operating hours of the LHP were accumulated during the 16 day mission. Testing consisted of numerous start-ups, step power changes ranging from 15 to 400 Watts, 18 hours steady state operation at low power (20 W), 49 hours steady state operation at high power (200 W), and temperature control tests using a built-in thermostat. The operating temperatures of the loop ranged from -27°C to +66°C; the lowest sink temperature was -34°C. All objectives of the test plan were met or exceeded. The LHP functioned flawlessly throughout the entire test program.