The infrared photolysis of polyatomic molecules is discussed. Several examples are presented, with products being detected either by chemiluminescence or by laser-induced fluorescence. The technique allows a study both of the dynamics of unimolecular decomposition and of the reaction kinetics and dynamics of the resulting free radicals. Information on the former is deduced from such features as product energy partitioning, product yield as a function of incident laser fluence, and the effect of collisions on the degree and rate of the dissociation. The latter aspect of the technique is powerfully illustrated by the reactions of C2 (X,a) radicals (produced by photolysis of several organic molecules) with such gases as 02 and NO, from which chemiluminescent reaction products have been detected.