Abstract: A method for testing a printed circuit board to determining the dielectric loss associated with the circuit board material relative to a standard. Dielectric losses in the material generate heat when a high frequency electronic signal, such as a microwave frequency signal, is communicated through a microstrip that is embedded within the printed circuit board. The temperature or spectrum at the surface of printed circuit board is measured and compared against the temperature or spectrum of the standard to determine whether the material under test is acceptable. While various temperature measurement devices may be used, the temperature is preferably measured without contacting the surface, such as using an infrared radiation probe.