A lattice fluid theory valid from pure fluids to multi-component mixtures Of Molecules having any number of associating donor and acceptor groups formulated. Under the fundamental assumption that the intermolecular forces are divided into physical and chemical forces, the Veytsman statistics for associating contribution was combined with the multi-fluid nonrandom lattice fluid (MLF) equation of state developed recently by the present authors. The physical contribution is characterized by temperature independent molecular parameters representing close packed volumes of a mer, segment numbers and energy parameters of a pure fluid, and a binary interaction parameter for a binary mixture. The chemical part is represented by internal energy and entropy of associating system. The resulting multi-fluid nonrandom associating lattice fluid (MALF) equation of state was applied to describe thermodynamic properties of pure fluids and phase equilibrium Of Mixtures. The results for alkane-alcohol and alcohol-alcohol mixtures were found satisfactory for most systems when compared with the MLF and the statistical associating fluid theory (SAFT) model. (c) 2007 Elsevier B.V. All rights reserved.