In this work the EPR spectrum of copper orotate single crystals Cu(C5H2N2O4)(H2O)2 was investigated. At room temperature the EPR spectrum of copper orotate has a single line with rhombic anisotropy. The extremal values of effective g-factor were obtained. The low-temperature broadening of resonance line which may be connected with short-range magnetic order was established.The orotic acid is the predecessor of the pyrimidine bases of nucleic acids at their biosynthesis. The biotransformational reactions of an orotic acid are realized in the presence of enzyme. The metal ions are necessary for their activation and normal functioning. Series of works [1-2] devoted to the interaction of metal ions with orotic acid and its derivatives has been recently published. The main attention was given to the interrelation between chemical properties of metal ions and their role in life of organism.Copper orotate [Cu(C 5 H 2 N 2 O 4 )(H 2 O) 2 ] belongs to the family of metallo-organic substances used in medicine as complexes, having enzyme properties. For finding out the general laws of reactions with enzyme the establishment of metal-organic complexes equilibrium structures is necessary. Thus, the most of information we obtained from the study of EPR spectra of Cu 2+ ions in similar metal-organic complexes.In this paper we report the measurements of angular and temperature dependences of EPR spectrum of Cu 2+ ions in a copper orotate single crystal. Because of the weak bond between molecules in a crystal it is possible to assume small distinction in coordination of Cu 2+ ions in crystals of orotic acid salts and biological solution [3]. Therefore it is possible to consider that Cu 2+ ions spectra in crystal and biological solution are identical.Blue-green colored single crystals of copper orotate belong to monoclinic space group P2 1 /n with parameters a = 9.503Å, b = 6.9147Å, c = 11,851Å, β = 95.22 o , z = 4, V = 775.5Å 3 . The parameters of unit cell and intensity of reflections are measured on an automatic diffractometer Siemens P3/PC [4]. From the analysis of * ) Presented at 12