We have detected free radicals in the gas-phase smoke resulting from the combustion of several household materials. Materials were pyrolyzed by rapid heating in a quartz ignition tube in a flowing air stream. The filtered smoke was bubbled into a dodecane solution of alpha-phenyl-N-t-butylnitrone (PBN), and the resulting nitroxide radicals were detected by electron spin resonance. Cellulosic materials (birch plywood, cellulose, 1R1 research cigarette tobacco, and yellow pine) and dried exterior paint produce about the same yield of trapped radicals. The smoke from polyethylene and rubber produce approximately 2-fold more radicals than the smoke from the cellulosic materials. Nylon smoke yields about 10-fold less radicals than the cellulosic materials. The smokes from polyvinyl chloride and polytetraflouroethylene do not produce detectable spin adducts of PBN by this method. Where radicals were trapped, oxygen-centered spin adducts predominated; lesser amounts of carbon-centered spin adducts and an oxidation product of PBN were observed. Different oxygen-centered radicals were detected from different materials, as judged from the variation observed in the hyperfine splitting constants of the principal spin adducts. When cellulose smoke is dissolved in solution, radicals continue to be produced for at least 20 min, suggesting the production of a metastable species in the gas phase that decomposes to form radicals in solution.