Abstract: The invention relates to the field of drug development against acute radiation injury caused by exposure to high-energy electromagnetic waves (X-rays, gamma rays) or particles (alpha particles, beta particles, neutrons). To date, there is no effective drug to ameliorate radiation injury after accidental exposure to ionizing irradiation. The invention provides a method of treating radiation injury of a subject in need thereof comprising administering to the subject a peptide, or functional analogue or derivative thereof, of smaller than 30 amino acids. Furthermore, the invention provides use of a peptide, or functional analogue or derivative thereof, of smaller than 30 amino acids for the production of a pharmaceutical composition for the treatment of a subject suffering from or believed to be suffering from radiation injury. In particular, the invention provides anti-radiation peptides having a dose reduction factor (DRF) against acute gamma irradiation of at least 1.