Electrical conductivity of potassium chloride solutions containing polyethylene glycol (PEG) of different molecular mass was measured in a wide range of the polymer concentration up to 33 wt. % for PEG 300, 600, 2000, 4600, and 10 000. The data were used to find the dependence of microviscosity, eta(micro), which characterizes the decrease of the ion mobility compared to that in the polymer-free solution, on the polymer volume fraction, phi. We find that the dependence is well approximated by a simple relation eta(micro)/eta(0)=exp[kphi/(1-phi)], where eta(0) is viscosity of the polymer-free solution and k is a fitting parameter. Parameter k weakly depends on the polymer molecular mass growing from 2.5 for PEG 300 to its limiting value close to 2.9 for long chains. Using the phi-dependence of microviscosity, we give a practical formula for the conductivity of PEG-containing electrolyte solutions. (C) 2003 American Institute of Physics.