The multiline behavior of a ballast resistance helical TEA CO2laser incorporating hot CO2as an intracavity absorber has been studied. Simultaneous laser oscillation on , and lines of 10.6 μm has been obtained reliably. A rate equation model has been developed for the hot CO2absorber and is incorporated with the model for the multiline TEA CO2laser for calculating laser intensities on , and lines of the 10.6 μm band in the presence of the absorber. The theoretical calculations agree quite well with the experimental observations. These studies show that a hot CO2column of Proper length and temperature inside a TEA CO2laser cavity can produce simultaneous laser oscillation on at least three rotational lines , and of the 10.6 μm band with almost equal intensity.