The paper summarizes Session I papers (given at the EPA Workshop on Characterization of Contaminant Emissions from Indoor Sources, Chapel Hill, NC, May 1985) that illustrate the progress made to date on characterizing indoor combustion emissions from unvented space heaters, gas appliances, and sidestream cigarette smoke. The state of knowledge of such emissions and their controllability is summarized by four general statements: (1) Unvented gas-fired appliances are important sources of indoor CO and NOx, but not of organic emissions; (2) Important combustion sources of indoor organics, include smoking and possibly kerosene heaters; (3) The extent of the problems of leakage from vented appliances is simply not known; (4) Indoor combustion sources do not appear to present major problems with controllability, if source removal is an acceptable alternative. From an engineering standpoint, the most challenging issue is burner design changes for unvented appliances.