Melt viscosity eta at 25-degrees-C of four oligomeric triblock copolymers consisting of a central block of ethoxamer units and two end blocks of propoxamer units (PEP) (M(n) X 10(-3) = 1 and 2; mole fraction of ethoxamer units x(E) = 0.41, 0.57, and 0.74) was analyzed in terms of the theory advanced by Berry and Fox. The structure-dependent factor F(X) was deduced from the intrinsic viscosity data, and the mean friction factor per friction center zeta was computed from eta and F(X). At a fixed molecular weight, it increases with increasing x(E). The dependence of zeta versus x(E) was compared with curves computed from the data for homopolymers. The best agreement was obtained if the following values of the inherent friction factor (log zeta(0) were used : -10.25 for poly(ethylene oxide) PEO and -10.65 for PPO.