Foam plastic building materials were exposed to practical fire environments. Toxic gases evolution from various foam plastic boards burning under fire conditions involving plywood combustion was determined. A foam plastic board as a specimen lined on one of the inside walls of a "plywood box shape" was combusted in a semifull-scale fire test room under different air sypply rates. CO was the most important toxicant, followed by HCN and acrolein. The difference in maximum total toxicity acording to the fire test was rather small, probably because the toxicity from plywood accounted for a large portion of the total toxicity. However, the maximum total toxicity indexes of combustion gases involving rigid urethane and polyisocyanurate foams were higher than when phenolic and polystyrene foams were involved in fire tests, because a considerably great amount of HCN was produced from the above nitrogen-containing materials.