Аннотация:The determination of which of the indicated factors plays the most essential role in laser ignition of metals is of interest. For this purpose, the effect of the heat of the exothermic reaction on the development of thermochemical instability was investigated. Laser heating of a metal target in an oxidizing atmosphere with consideration of the intrinsic heat of reaction is described in the equations used. The concluding formula shows how the decrease of tau /SUB alpha/ occurs during a gradual increase of the intrinsic heat of reaction before this leads to a quantitatively new effect of occurrence of threshold, represented as an equation in the paper.