Aspects of the heating, ignition and extinction of an AP/HTPB (86/14) composite propellant, induced by means of a CO2 laser energy pulse, are investigated in the subatmospheric pressure range to determine the influence of the operating conditions on these processes. Measurements of the ignition delay time and ignition temperature for any operating condition have been done by microthermocouples able to record the temperature history of the irradiated surface and of the gas phase. Determinations of the boundaries location, defining the propellant behavior after the external energy removal, by the go-nogo techniques, have permitted to evaluate the minimum exposure time which assures to avoid the propellant extinction after the propellant ignition. Combustion transients have been studied to determine the burning propellant response to the laser energy pulse and to define the pulse features which yields the propellant extinction for different working pressure. Laser Doppler Velocimetry (LDV) technique, able to measure the velocity of the gas coming out from the burning propellant surface, was used to follow the whole combustion transient giving a precise picture of the phenomenon. Comparisons between data obtained studying the ignition and extinction by laser energy pulse phenomena show that the operating pressure has opposite effects on the propellant response to the external energy input having the same characteristics.