Isothermal vapor-liquid equilibria were measured for three binary systems of 1-butanol + octane at 373.15 K, 2-butanol + octane at 358.15 K, and 2-methyl-2-propanol + octane at 343.15 K. The measurements were made in a Rogalski-Malanowski type equilibrium still with circulation of both the vapor and liquid phases. Three binary isothermal systems form a maximum pressure azeotrope. The azeotropic data are x(1)(AZ) = 0.519 mole fraction and P(AZ) = 75.71 kPa for 1-butanol (1) + octane (2), x(1)(AZ) = 0.750 mole fraction and P(AZ) = 63.58 kPa for 2-butanol (1) + octane (2), and x(1)(AZ) = 0.968 mole fraction and P(AZ) = 61.18 kPa for 2-methyl-2-propanol (1) + octane (2). The activity coefficients of three binary systems were correlated with the Wilson, modified Wilson, nonrandom two-liquid (NRTL), and UNIQUAC equations.