Experimental isothermal (P-x) data at T = 313.15 K for the binary (1-butanol + 1-hexene) and ternary (1-butanol + 2,2,4-trimethylpentane + 1-hexene) systems are reported. The measurements have been performed with an isothermal total pressure cell. Data reduction by Barker's method provides correlations for G(E), using the Margules equation for the binary system and the Wohl expansion for the ternary system. Wilson, NRTL, and UNIQUAC models have been applied successfully to the data correlation of the binary and ternary systems. The mixtures investigated exhibit positive deviation from ideal behaviour. Good results are obtained for the correlation by all the models. (C) 2013 Elsevier Ltd. All rights reserved.