Binary (vapour + liquid) equilibrium data were obtained for the {1, 1 -difluoroethane (HFC-152a) + n-butane (HC-600)}system at temperatures from 313.15 K to 363.15 K. These experiments were carried out with a circulating-type apparatus with on-line gas chromatography. The experimental data were correlated well by Peng-Robinson equation of state using the Wong-Sandler mixing rules. This system shows positive azeotropic phase behaviour. (c) 2006 Published by Elsevier Ltd.