The electron paramagnetic resonance parameters (g factors g||, g⊥ and zero-field splitting D) of the approximately tetragonal defect centre, FeZn+-X, in cubic ZnS crystal were calculated from high-order perturbation formulae based on the two spin-orbit coupling parameter model for the electron paramagnetic resonance parameters of the 3d7 ion in tetragonal symmetry. From the calculations, it was suggested that the associated defect X (which was at the interstitial site on a <100> axis, but its origin and nature remain unknown) in this centre has a negatively charged state (i.e. an anion). The slightly monoclinic distortion of this defect centre was attributed to a further anion S2- vacancy Vs2- in the vicinity of defect X owing to charge compensation.Defect Model and Electron Paramagnetic Resonance Parameters of an FeZn+-X Complex Defect in ZnS Crystal. W.C.Zheng, X.X.Wu: Journal of Physics D, 2005, 38, 4157-9