Glucose oxidase was immobilized into photographic gelatin hardened by chromium(III) sulphate. The enzyme-gelatin mixture was coated on polyester film strips which allowed easy and simple handling during assays. The effect of gelatin and cross-linker concentrations on water content and enzymatic activity was studied. The effect of pH during immobilization and that of incubation temperature on maximum activity were examined- Enzyme leakage tests were carried out during reuse number studies. Consecutive use of strips followed by washing and resting between uses were found to affect the reuse number. A maximum immobilization of 68% was reached under optimal conditions. Mechanical stability and leakage were found to be functions of gelatin and cross-linker concentrations. Photographic gelatin was found to have many capabilities with extraordinary characteristics as a carrier on immobilization.