Peroxidases (PODs) were localized in pumpkin tissues by using an immune-gold labeling technique in combination with transmission electron microcopy (TEM). Polyclonal antibodies raised in rabbits against horseradish peroxidase were utilized. The localization patterns of gold particles for peroxidases from tissues of both control and gamma-irradiated plants were typically present in the plasma membrane, cytosol, and cell walls. However, particle densities were remarkably increased on the cell corner middle lamellae of parenchyma cells, especially in the petioles. Based on these results, we propose that growth inhibition is associated with cell-wall stiffening, as related to the formation of cross-links among cell wall polymers. In addition, the densities of POD following gamma irradiation vary according to cell and tissue types in pumpkin.