The Knudsen mass-loss effusion technique was used to measure the vapour pressures at different temperatures of the following substituted benzoic acids: 2-amino-3-methylbenzoic acid at T between 343.16 K and 357.17 K; 2-amino-5-methylbenzoic acid at T between 345.15 K and 361.16 K; 2-amino-6-methylbenzoic acid at T between 339.17 K and 355.15 K; 3-amino-2-methylbenzoic acid at T between 367.16 K and 381.22 K; 3-amino-4-methylbenzoic acid at T between 363.18 K and 377.16 K; and 4-amino-3-methylbenzoic acid at T between 367.17 K and 383.14 K. The standard, P-0 = 10(5) Pa, molar enthalpies, entropies, and Gibbs energies of sublimation at T = 298.15 K were derived from the temperature dependence of the vapour pressure using estimated values for the heat capacity differences between the gas and the crystal phases of the studied compounds. [GRAPHICS]