Abstract: Organic polymeric substrates, for example polyolefins such as polypropylene, can be made flame retardant by the incorporation of a synergistic mixture of (i) at least one sterically hindered alkoxyamine stabilizer and (ii) at least one conventional flame retardant selected from the group consisting of the melamine based flame retardants. The compositions of the invention combine good flame retardant properties with light stability and good mechanical properties. Polyolefin molded articles are stabilized against light, heat and oxygen and made flame retardant with the incorporation of at least one sterically hindered alkoxyamine and at least one conventional flame retardant, while allowing normally high levels of flame-retardant fillers to be greatly reduced or eliminated.