The influence of gamma-radiation on the molecular characteristics of low-density polyethylene dependant on the samples' thickness, the intensity and the dose has been investigated by methods of viscosimetry and light scattering. A remarkable increase of molecular mass by the increase in radiation doses was established. It is linear for the mass-average molecular mass while for the viscosity average molecular mass it is minimum at the initial doses. The origin of this minimum is explained by the change of macromolecular hydrodynamic volume, as it has also been established that the growth of molecular mass at the initial doses is mainly due to the increase of the degree of macromolecular branching. A dependence of the rate of change of polyethylene molecular characteristics on the samples' thickness, irradiation intensity and dose was established.