Drag reduction in turbulent Bow of high-molecular-weight polymer solutions has been investigated. Experiments were run in a rotational apparatus with geometrically similar operating units of different sizes. Aqueous solutions of poly(ethylene oxide) with different molecular weights and solutions of polyisobutylene in kerosene were used. The concentration and temperature of the solutions were varied. Drag reduction was correlated with the rheological characteristics of the solutions; i.e. with the natural time and the shear-thinning viscosity. The dimensionless viscoelastic parameters have been found, which, with the Reynolds number, determine the turbulent friction. These are the Weissenberg number and the relative amplitude of the shear-thinning viscosity. Drag reduction sets in at a certain value of the local Weissenberg number calculated from turbulent Bow characteristics near the wall. The critical value of this criterion is equal to several units. Friction coefficient versus Reynolds number functions are of a power nature with the exponent depending on the relative amplitude of the shear-thinning viscosity. Empirical relations were obtained that can describe fluid friction of the polymer solutions in dimensionless form.