Triphenyl phosphate and a brominated phosphate were compared as flame retardant additives for polycarbonate/ABS blends. The concentration of the flame retardant was varied from 6 to 14% and the polycarbonate/ABS ratio was varied from 3/1 to 1/l. A commercial polycarbonate/ABS blend is 3/1 with about 14% triphenyl phosphate for a UL-94 V-0/5V rating. Reducing the polycarbonate or the flame retardant level gives products which do not pass UL-94 V-O/5V. Compositions containing the brominated phosphate with UL- 94 V-O/5V ratings include use of 6% flame retardant or 14% flame retardant with polymer ratios down to 1/1. Cone calorimetry data show significantly longer time to ignition, lower total heat release and lower peak heat release rate for the brominated phosphate-containing resin. Mechanical properties are also given.