The conformation changes in DNA in water ethanol solutions (ethanol content 0-22 wt.%, ionic strength μ = 0.15 M NaCl) exposed to γ radiation (10 Gy and 30 Gy doses) were investigated by low-gradient viscosimetry, birefringence in a flow, circular dichroism (CD), and UV spectrophotometry. For μ = 0.15 M, the volume of intact DNA remained constant over the whole range of alcohol concentrations studied in contrast to water alcohol solutions of lower ionic strength, in which the specific volume of the macromolecule decreased cooperatively at a critical concentration of alcohol corresponding to a structure disturbance of water (C _cr = 16.5 wt.% for ethanol). Inversion of the dependence of the specific volume of DNA on the radiation dose, which was found previously for water alcohol solutions with μ = 0.003 M NaCl, vanished under these conditions. For μ = 0.15 M, the dependence of V _sp of DNA on C _eth had no features at C _eth = C _cr; at C _eth ≥ 1.7 wt.% the volume of the macromolecule did not change after irradiation with doses of up to 40 Gy. This is probably explained by the fact that at high salt concentrations the alcohol loses its influence on the structure of the solvent, and its role in the process of γ irradiation is restricted to interception of the active products of water radiolysis.