Polypyrrole heparin composite conducting polymers (PPy/heparin) have been electrochemically synthesised on a quartz crystal electrode. PPy/heparin is electro-active and shows cation exchange properties upon reduction/oxidation. The immobilised heparin can be determined using the toluidine blue assay. Electrochemical quartz crystal microbalance studies show that the heparin in the composite polymer is still active in binding thrombin. In contrast, PPy/heparin has no specific interaction with other test proteins such as BSA or HSA. The morphology of the PPy/heparin composite was investigated using atomic force microscopy.