Many materials of rubber, plastic, and resinous composition are not adapted to infrared analysis by conventional techniques because of their physical intractability. The dry distillation products of these complex materials frequently will permit the preparation of a reproducible infrared spectrum which will be characteristic of the original material, reveals the applications and limitations of the method. Several examples of the pyrolyzate- infrared approach to typical problems are given to illustrate the unusual rapidity and utility of the procedure as compared to any other known method.