[en] Stable nitroxyl radicals with common formula RN-O (here R is fragment of molecule, which can give to it particular properties) are widely used as 'spin' markers for study of molecular dynamics. Nitroxyl group N-O which has the uncompensated electron is well registered by the EPR spectroscopy method. The dependence of the EPR signal intensity of nitroxyl radical via time of exposure in various solvents was studied. For all solvents the dependence of the EPR signal intensity has linear site. The dependence of reduction rate of the EPR signal intensity of nitroxyl radical via solvent polarity at influence of gamma-irradiation is observed. The obtained experimental data evidence about formation of molecular complexes of nitroxyl in solutions the formation energy of which depends on polarity of solvent. The question about formation energy and structure of complexes is not decided. However it is clear that these systems can be perspective chemical dosimeters