The dependence of the critical volume fraction at constant pressure as function of the chain length of a polymer solution can be described by a power law. In a recent investigation of the chain length dependence of the critical volume fraction, a correlation equation for the critical volume fraction has been proposed. This equation combines the Flory and the renormalization models. Here, the new equation is extended to polymer blends and applied to the correlation of several experimental datasets for polymer solutions and one dataset for blends obtained from an equation of state for retrograde liquid-liquid immiscibility. The analysis of the polymer blend data in terms of the exponent of the power law shows qualitatively different behavior as for polymer solutions. (C) 2003 Elsevier B.V. All rights reserved.