Updated project metadata. The population's increasing risk of acute large-scale radiological/nuclear exposures underlines the need for functional radiation biomarkers. As ionizing radiation triggers a complex response on the genome, proteome, and metabolome level, all were already reported as suitable indicators of radiation-induced damage in vitro or in animal models. We aim to analyze the blood of total-body irradiated (TBI) leukaemia patients using a mass spectrometry approach and to identify and quantify plasma proteins before and after irradiation. Combining two independent mass spectrometry approaches we identified 15 plasma proteins differing in the blood of TBI patients before and after irradiation. The majority of proteins were associated with the inflammatory responce of the immune system and with metabolism of lipids. These candidate radiation biomarkers might have implications for practical biological dosimetry.