Vapour pressures of (1-chlorobutane + 1-butanol, or 2-methyl-2-propanol) at several temperatures between T = 278.15 and T = 323.15 K were measured by a static method. Reduction of the vapour pressures to obtain activity coefficients and excess molar Gibbs energies was carried out by fitting the vapour pressure data to the Redlich-Kister equation according to Barker's method. For (1-chlorobutane + 2-methyl-2-propanol) azeotropic mixtures with a minimum boiling temperature were observed over the whole temperature range.