Electrical and thermal behavior of the carbon fiber polymer matrix composites subjected to time-varying and steady electric currents is studied. A fully automated experimental setup for real time measurements of the electric current, resistance, voltage, and temperature in carbon fiber polymer matrix composites has been developed. A series of electrical characterization tests on IM7/977-3 unidirectional and symmetric cross-ply composite laminates have been performed and the effects of electric current magnitude and duration, electrical resistance, and associated thermal effects have been investigated. It is determined that voltage-current relationship stays ohmic for up to 50 A steady currents, electrical resistance exhibits time-dependent behavior. It is also found that application of an electric current leads to a significant temperature rise in the composites that is a result of the intense Joule heat produced in the electrically conductive carbon fibers as well as in the composite-electrode contact.