A review with 137 references covering polymers endowed with photo- and electroluminescent properties and applicable in organic light-emitting diodes (LED). Chemical modifications of monomers and polymers are discussed, intended to result in improved electroluminescent, mechanical and processing properties of the organic LEDs. Of major importance are poly(p-phenylene) (PPV) and poly(2,5-thiophene)s, i.e., polymers with coupled double bonds. Polymers containing isolated chromophore groupings either as segments of the main chain (e.g., compounds XXXI - XXXIII) or as side chains (e.g., compounds XXXVII, XXXVIII), are also discussed.