CORM-3 is a water-soluble CO-releasing carbonyl complex.A low concentration of CO has been proved to be involved in the protection against cell death and oxidative injury,anti-inflammatory and anti-apoptotic effects,control of cell proliferation,tolerance of organ transplantation and neurotransmission[1].Using a zebrafish model,this study was designed to investigate the protective effects of CORM-3 on the developmental toxicity in zebrafish embryos induced by ionizing radiation with different linear energy transfer(LET).