Acoustic emission is a simple nondestructive technique for monitoring the onset of failure of materials under mechanical strain under laboratory conditions or in actual service. When release of strain in a material takes place, for example, by cracking in the bulk material or at a bonded interface, some of the strain energy released generates stress waves which travel through the bulk of the material and may be detected by sensitive transducers which respond to the consequent surface displacement. The novel application of this technique to monitoring failure mechanisms in paint films during service is described. Illustrative examples show the application of the technique to the study of weathering and failure in decorative paints and to the detection of failure in car paint systems. (Abstractor's note: The details of the nondestructive test method are not given in this article. The technique could be used to study art objects and in conservation treatments.) -- AATA