Scaling in terms of temperature, composition, and molecular weight variables has practical and fundamental significance. The hydrodynamics of hard sphere systems suggest the scaling of the dimensionless ratioηsp/(c[η])in terms of a concentration parameterγ(M,T)=1/[η].Solutions of flexible chains indicate the appropriateness of this equation at θ and sub θ conditions, but otherwise a molecular weight dependence of γ differing from that of[η]−1.It is possible however to define a corresponding states principle through an empirical relation between γ andM.In this case1/γ∝kH[η],withkHthe Huggins parameter. This scheme extends in some cases up to the melt. One of us (L.A.U.) has previously considered melt viscosities of low and high molecular weight systems in terms of free volume concepts, combined with theoretical liquid state results, and withTgscaling the temperature. An extension to solutions yields an explicit viscosity‐concentration‐temperature function. Gratifying agreement with experiment can be seen. Structural changes, generated by temperature, concentration, and pressure changes, are reflected in the scaling parameters.