Abstract Experimental evidence is reported for the IR multiple-photon dissociation of O 3 and OCS. A pulsed UV-laser permitting a time resolution of 20 ns was used to follow the decomposition of O 3 after an intense CO 2-laser pulse. Dissociation continues several μs after the end of IR excitation. OCS was dissociated in a molecular-beam experiment. The threshold intensity is 1.3 × 10 8 W/cm 2 with the P24 line in the 9.6 ωm band of the CO 2 laser.