A simple procedure to immobilize chloroplast using water-soluble poly(vinyl alchol) substituted with 1 mol% of 4-styrylpyridinium residue is described. An air-dried film of the photosensitive poly(vinyl alchol) containing chloroplast was reinforced by a polyester gauze and exposed to uv light for a few minutes. The chloroplast entrapped in the insolubilized film showed remarkable stability on storage in the dark. Co-immobilization. of glucose oxidase and catalase was performed to decrease the rate of the inactivation of the chloroplast on illumination.