Abstract: This invention relates to flame retarding compositions comprising flame retardants selected from pentate salts and nitrogen-containing phosphates wherein one or both are encapsulated in a material to reduce contacts between the flame retardants during processing and to thus reduce or eliminate pre-reaction between the two flame retardants, which pre-reaction, normally leads to degradation of flameproofing properties of the compositions. The invention is also directed to flame retardant polyurethane compositions containing a polyurethane resin and both of the flame retardants. As between the flame retardants, amount of the phosphate is about 10-99% whereas amount of the pentate salt is about 90-1%, on weight basis. In the polyurethane compositions, combined weight of the two flame retardants is about 10-60%, based on the weight of the polyurethane resin and the two flame retardants.