Plant regeneration through organogenesis of shoot bud from callus cultures of strawberry was established and three types of callus having different regeneration capacity were obtained. This experimental system was used to investigate the release of peroxide radicals and hydrogen peroxide, and the activities of antioxidant enzymes. H2O2 production coincided with emergence of meristemoid and formation of bud primordium in morphogenic calli. During the differentiation and development of callus, superoxide dismutase (SOD) activity increased in the early regeneration culture and decreased thereafter, and catalase activity constantly declined while peroxidase decreased during the 5-d culture and gradually increased thereafter. High O2.- level, low H2O2 level and nearly no SOD activity were detected in calli possessing low organogenesis capacity. N,N-diethyldithiocarbonate treatment decreased the regeneration percentage, while exogenous addition of H2O2 slightly promoted the potential for regeneration of shoot bud. The results suggest that H2O2 is correlated with the morphogenetic process in strawberry callus, and may actually serve as a messenger in the process of bud primordium formation.