The gas phase bromination of polyethylene (PE), polypropylene (PP) and polystyrene (PS) film surfaces by free radical photochemical pathway occurs with high regioselectivity. The surface bromination was accompanied by simultaneous dehydrobromination resulting in the formation of long sequences of conjugated double bonds. Thus, the brominated polyolefin surface contains bromide (Br) moieties in different chemical environments. The formation of Br moieties on the brominated polyolefin film surfaces was shown by XPS and ATR-FTIR analysis and long sequences of double bonds by UV-Vis spectroscopy. For comparison, gas phase free radical photochemical chlorination of polyolefin films was also examined. The results show that, chlorination proceeds in a relatively random way and it is also accompanied by simultaneous dehydrochlorination. (C) 2000 Elsevier Science Ltd. All rights reserved.