The results of numerical simulations of elongating the pulse duration of a TEA CO 2 laser are reported. It is shown that neither relative increase of N 2 gas in the N 2 :He:CO 2 gas mixture nor elongation of the pulse duration of the discharge current is very effective. A significant result is obtained with the pulse injection locking method, when the following two conditions are satisfied: 1) the detuning angle is less than 0.1π, and 2) the initiation of discharge of the main laser is synchronized with the injected laser pulse within about 200 ns.