A study has been made of immobilization of collagen to polystyrene resulting from ion bombardment. Type-I collagen was coated onto PS plate and bombarded with 50-keV He + ions at doses between 1x10 1 3 and 1x10 1 5 ions/cm 2 . The collagen-coated surfaces were mounted on parallel-plate flow chambers, with a flowing shear stress of 2 Pa for 1 h, in a flow system prepared for tests of collagen adhesion. The rate at which collagen peeled off due to the flowing shear stress was evaluated by comparing IR absorption of collagen before and after the test. Morphology observations using transmission-electron microscopy and atomic force microscopy were performed in order to investigate the mutual relationship between collagen adhesion and morphology.