Repetitive pulsing of the CO2laser has been obtained as a result of absorption by formic acid vapor, propylene gas, heated CO2gas or heated CO2‐propylene mixtures. Pulsing rates of close to 105pulses per second have been obtained. Remarkable stability in the frequency and amplitude of the pulses has been observed. Any CO2line can be pulsed without difficulty, and it is suggested that a proper match of absorber lines and laser lines should permit pulsing of other types of infrared lasers.