The experimental investigations of laser-induced ignition and heat action of ammonium perchlorate and aluminum powder mixtures are presented in this paper. A laser pulse with wavelength of 1.06 mu m and duration of 3.5 ms was used. Powder mixtures of different dispersion were tested, namely, coarsely dispersed powders and nanopowders with average surface diameters of 80 and 0.25 mu m, respectively. The values of ignition thresholds and delays of the mixtures activity in air were measured, and experimental results for different exposure conditions were obtained. The possible reasons of different sensitivity for the given mixtures to laser pulse and heat action are discussed.