The control of tail skin temperature in mice was evaluated with transient and frequency analysis using 2,450-MHz microwave radiation and ambient temperature as thermal stimuli. Restrained mice at an ambient temperature (Ta) of 21 C were exposed to 2,450-MHz microwaves at incident powers of 0.18, 0.37, 0.56, or 0.74 W and Ta increments of 2, 4, 6, or 8 C. During thermal stimulation, tail skin temperature increased in either an overdamped manner with no overshoot or moderately damped with some overshoot over its settled, steady-state level. The natural frequency of skin temperature, calculated from response time and overshoot, was 0.0004-0.0006 Hz. A Bode plot for skin temperature was constructed by exposing mice to square-wave pulses of microwave radiation at frequencies of 0.00027-0.0055 Hz. The corner frequency of the Bode plot, where gain is attenuated, was 0.0006 Hz. The frequency and transient response of skin temperature control are far below that of most other physiologically controlled systems. Although the control of skin temperature is a nonlinear system, it is shown that frequency and transient analysis is a useful method for describing overall control of skin temperature.