Basic characteristics of an electroopticallyQ-switched CO2laser are given in this paper. Studies of the dynamics ofQswitching using this system are compared with solutions of classical rate equations, clarifying the role of various processes in determining the output characteristics.Qswitching was obtained with an intracavity GaAs modulator crystal. Outputs similar to those of other switching techniques are obtained but with greater time control and somewhat greater amplitude stability. The pulse shape and the delay between switching and pulse development are independent of the manner in which switching was obtained, due to the fast ( < 1 ns) switching capability of this technique. Data on the dependence of these parameters on cavity losses are given. Comparison of these data with solutions of rate equations shows that stimulated emission and resonator losses alone are important in early pulse development. However, to describe adequately the entire pulse shape, it is shown that the effect of rotational thermalization in the CO2molecule must be included in the rate equations.