This study determined the experimental relative permittivity data for the (1,3-butanediol + 1-octanol) and (1,3-butanediol + 1,4-dioxane) binary systems as a function of composition at T = (298.2, 303.2, 308.2, 313.2, and 318.2) K. The permittivity deviations were correlated using the Redlich-Kister polynomial equation for the estimation of the binary coefficients and the standard errors over the range of temperature studied. The Guggenheim-Debye method was used to evaluate the molecular dipole moments of the liquids throughout the investigated temperature range. The effective dipole moments of the pure and their binary mixtures were also studied using the experimental results. In this work, the excess parameters such as the excess permittivity and the excess Helmholtz energy were calculated. The results are discussed in terms of homo and hetero interactions and structure of the studied binary mixtures. In order to predict the permittivity data of the polar-nonpolar binary system consisting of 1,3-butanediol and 1,4-dioxane, six theoretical models were applied. (C) 2013 Elsevier Ltd. All rights reserved.