Abstract: A temperature-controlled chamber comprises a portable, insulated housing with an internal cavity shaped to receive a container of temperature-sensitive material therein, such as insulin, antibiotics, or the like. A thermoelectric element, or heat pump, has one face in heat-transfer relation with the housing cavity, and the other face connected with a heat exchanger having an exterior portion exposed to the atmosphere. A source of electric power is coupled to the thermoelectric element through a thermostat control which energizes the thermoelectric element in response to temperature fluctuations in the housing cavity. The thermostat control includes switching means to reverse the polarity of the power supplied to the thermoelectric element as a function of whether the sensed temperature in the housing cavity is too high or too low, to alternatively heat or cool the housing cavity as required to maintain the cavity at a generally constant temperature.