Abstract: The present invention relates to fire retardant polymer compositions possessing a non-liner structural configuration resulting by the reaction of N-tribromo-phenylmaleimide, with or without comonomer, with a preformed backbone polymer, in which the bromine content is above 1.2% by weight bromine. The polymer is selected from polystyrene, polyolefins, polyamides, rubbers, polyesters, acrylics, polymeric dienes and mixtures or copolymers thereof. The comonomer present with the N-tribromophenyl-maleimide is selected from the group consisting of acrylonitrile, styrene and vinyl chloride. According to the invention the non-linear structural configurations are obtained either by grafting or crosslinking of the N-tribromophenylmaleimide onto the preformed backbone polymer in the presence of free radical producing means. Optionally, synergistic fire retardant additives such as antimony oxide are incorporated in the compositions.