This review provides insight into the ignition, combustion, smoke, toxicity, and fire-retardant performance of flexible and rigid polyurethane foams. This review also covers various additive and reactive fire-retardant approaches adopted to render polyurethane foams fire-retardant. Literature sources are mostly technical publications, patents, and books published since 1961. It has been found by different workers that polyurethane foams are easily ignitable and highly flammable, support combustion, and burn quite rapidly. They are therefore required to be fire-retardant for different applications. Polyurethane foams during combustion produce a large quantity of vision-obscuring smoke. The toxicity of the combustion products is Much higher than that of many other manmade polymers because of the high concentrations of hydrogen cyanide and carbon monoxide. Polyurethane foams have been rendered fire-retardant by the incorporation of phosphorus-containing compounds, halogen-containing compounds, nitrogen-containing additives, silicone-containing products, and miscellaneous organic and inorganic additives. Some heat-resistant groups such as carbodiimide-, isocyanurate-, and nitrogen-containing heterocycles formed with polyurethane foams also render urethane foams fire-retardant. Fire-retardant additives reduce the flammability, smoke level, and toxicity of polyurethane foams with some degradation in other characteristics. It can be concluded that despite many significant attempts, no commercial solution to the fire retardancy of polyurethane foams without some loss of physical and mechanical properties is available. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 1115-1143, 2009