Quasi-isochoric p rho T measurements on n-hexane/methanol mixtures were carried out in the low-density region by means of a constant-volume quartz glass cell. Eight isochores were measured in the temperature range from 347 up to 600 K at densities between 35 and 57 mol m(-3). Values of the second cross virial coefficient B-12 of n-hexane/methanol were derived and used to develop a correlation for the representation of its temperature dependence. The abilities of the scheme by Tsonopoulos, based on the theorem of corresponding states, and of the group contribution method by Brandani et al. were tested to predict B-12 for the n-hexane/methanol system. A relationship for the interaction parameter k(12) of the Tsonopoulos scheme was developed for binary mixtures of non-polar components with methanol. Furthermore, the parameter for the interaction between CH2 and CH3OH groups within the Brandani method was determined to be used for binary systems of methanol with n-alkanes.