The aqueous solution phase behavior of (ethylene oxide)/ethylene copolymers with varying degree of hydrophobicity is explored using an equation of state approach. The general formalism of the lattice-fluid with hydrogen-bonding theory is employed after a minor adjustment to account for multiple types of hydrogen bonds. The theoretical model is shown to be effective in describing the phase behavior of these systems, and the model parameters seem to be transferable between different homologous copolymer series. Despite limitations of the model, the calculated phase diagrams and the dependence of lower critical solution temperature (LCST) on the hydrophilic/hydrophobic content of the polymer show good correspondence with the available experimental data. (c) 2007 Elsevier B.V. All rights reserved.