Photoreactive insulin was synthesized by coupling with azidobenzoic acid. The insulin derivative was immobilized onto the wells of polystyrene culture plates by photoirradiation. The photoimmobilized insulin enhanced the growth of anchorage-dependent cells such as Chinese hamster ovary CHO-K1 and mouse fibroblast STO cells by more than native or azidophenyl-derivatized insulin. A small amount of photoimmobilized insulin (1-10% of the amount of the native or derivatized insulin) enhanced the growth of CHO-K1 and STO cells. In addition, the maximal mitogenic effect of the immobilized insulin was greater than that of native or derivatized insulin. Photoimmobilization could be a universal means of immobilizing growth factors onto the surface of materials devoid of chemical functional groups scaffolding growth factors and providing a new protein-free cell culture system or tissue engineering materials.