Gamma irradiated phosphoryethanolamine (C2H8NO4P) single crystals were investigated at 140 K using Electron Paramagnetic Resonance (EPR) technique. Phosphoryethanolamine single crystals have been irradiated with Co-60-gamma rays, at room temperature. The electron paramagnetic resonance (EPR) spectra of gamma irradiated phosphoryethanolamine single crystals have been studied for different orientations of crystals in a magnetic field. The spectra have been found to be temperature independent. The structure of the radical produced by gamma-irradiation of a single crystal of phosphoryethanolamine was discussed. The investigation of EPR spectra of gamma-irradiated single crystals of phosphoryethanolamine showed the presence of two radicals. One of the radicals is the H2PO4 neutral radical formed by the breakdown of the O(7)-C(8) bond. The other is the HPO4- anion radical formed by cleavage of the O(7)-C(8) bond and the attachment of an electron to O(2) by breaking H(1) bound to O(2). The principal values of the hyperfine coupling tensor of the unpaired electron and the principal values of the g-tensor and direction cosines of the radiation damage centers have been determined. The results were found to be in good agreement with the existing literature. (C) 2018 Elsevier B.V. All rights reserved.