With the advent of new millimeter-wavelength arrays such as the Atacama Large Millimeter Array capable of providing very precise maps of planetary emission, it becomes very critical to have an accurate knowledge of the millimeter-wavelength properties of gases under those planetary conditions. A millimeter-wavelength planetary atmospheric simulator and measurement system have been developed at the Georgia Tech Planetary Atmospheres Laboratory to accurately measure the propagation properties of gases under simulated planetary atmospheric conditions. The measurement system operates in the 2–4 millimeter-wavelength range and withstands up to 3 bars of pressure. It currently operates in the 190–300 K temperature range, and with minor modifications can operate in the 300–550 K temperature range for measurements of certain highly millimeter-wavelength-opaque gases. The measurements from this system can be used for developing accurate models of the millimeter-wavelength properties of gases under various planetary conditions which can then be used for retrieving the abundances of those gases through various remote sensing techniques.