A convenient method for the accurate measurement of Doppler temperatures as a function of time has been developed and applied to the C Stellarator. General agreement between Doppler and other temperature measures has been found when the plasma is quiescent. Late in the period of plasma containment however, the ion‐Doppler temperatures begin to fall appreciably below the electron temperature. This is shown to be explainable in terms of an influx of cold gas which tends to overcome the heating by the electrons.