A temperature tracking D.C. motor speed controlled fan (15) employs a temperature sensitive circuit element (35) to control the output voltage of a voltage regulator (24) which is applied as the D.C. input to the fan motor circuit (18). Typically, the voltage regulator (24) is an integrated circuit voltage regulator having an adjustable output voltage, variable as a function of circuit elements connected thereto. In each of several circuit arrangements, a thermistor (35) senses temperature to increase voltage and consequently fan speed with rising temperatures. In a preferred embodiment the thermistor is used to control the base drive of a transistor (Q 1 ) connected to the regulator. A Zener diode (0 2 ) connected in series with the transistor (Q 1 ) can provide a minimum output voltage from the voltage regulator, keeping the D.C. motor (10) of the fan turning at a low, quiet speed. The voltage applied to the thermistor (35) can be derived partly or wholly from the input to the regulator, reducing or eliminating the negative feedback effect that comes from deriving the thermistor voltage from the controlled output. A voltage stabilization circuit including a Zener diode (D 3 ) at the input to the voltage regulator can provide a stabilized voltage to the thermistor.