The invention provides methods and compositions for providing biocompatible surfaces to medical articles. In particular the invention provides biocompatible coatings with heparin activity. In some aspects, the biocompatible coatings of the invention are able to release a bioactive agent. The coatings can be formed using biostable or biodegradable polymeric material and photoreactive groups. The invention also provides methods for improving the quality of bioactive agent-containing coatings by performing pre-irradiation of biocompatible coating compositions.