Stable and repetitive single-longitudinal-mode output from a pulsed TEA carbon dioxide laser has been achieved using a time-gated gain cell. The gain cell is operated as an oscillator for the time periods between the laser pulses. Before the TEA laser is triggered, the gain cell is rapidly switched below threshold to avoid saturation of the gain-switched spike in the TEA laser pulse. Standard dither-stabilization techniques can be used during the CW operation of the gain cell to position the output coupler for single-mode operation. This method for obtaining single-mode output from a pulsed TEA laser is completely automatic and very straightforward to implement.