Polyphosphonates and phosphonate oligomers are a group of flame retardants that have gained much attention in recent years. Produced under the brand name Nofia,1 they are now commercially used to flame retard different resins such as polyesters, polycarbonate, polyurethanes, epoxies, unsaturated polyesters, and polyureas. Phosphonates can be used as the single flame retardant but recently, it was also shown, that phosphonates can support other non-halogenated and halogenated flame retardants. FRX Polymers has been screening many systems including replacement of antimony trioxide as the synergist in flame retardant formulations that are based on halogenated flame retardants. The present article discusses examples of the use of phosphonates in reinforced thermoplastic and thermoset applications.