Isozymes of peroxidase (POD), catalase (CAT), esterase (EST) and superoxide dismutase (SOD) were analyzed on transgenic maize (with external chitinase gene) and its parent by vertical poly- acrylamide gel electrophoresis (PAGE). This study was made using shoots at the fourth leaf stage. Results showed that: POD and EST were detected in 6 bands. POD-2 and POD-3 were present at the bud and seedling stages. POD-1, POD-4, POD-5 and POD-6 were only present at the seedling stage. POD-6 expressed stronger in the transgenic maize with chitinase than in its parent. EST-2 was pres- ent only at the bud stage, and its expression in transgenic maize was stronger than that in its parent. EST-5 only existed at the seedling stage. EST-4 did not exist in the parent maize seedlings and EST-1, EST-3 and EST-6 were present at the bud or seedling stage. Four bands were detected for CAT. CAT-1 and CAT-3 were weaker bands than the others. CAT-3 in transgenic maize was stronger than in its parent. Three bands of SOD were detected; SOD-1 and SOD-2 existed at the bud and seedling stages, but SOD-3 was not shown in buds of the parent corn. All data showed that the expression of isozymes in transgenic and parent maize had obvious differences.