In this work we introduce our continuum integral equation methodology to the study of alkane mixtures. The theory is applied to predict liquid-vapour coexistence properties in the mixed butane-heptane system using a model parameterization based only on the pure fluids. These predictions are in strong agreement with corresponding experimental values available for the mixture, including temperature composition phase envelopes, and temperature-pressure phase diagrams spanning a wide region of the system's overall coexistence regime. The alkanes are modelled as square-well chains, marking here our first application of the theory to chain mixtures with attractive interactions. (c) 2008 Elsevier B.V. All rights reserved.