Excess molar enthalpies and excess molar volumes of propionic acid + octane, + cyclohexane, + 1,3,5-trimethylbenzene, + oxane, and + 1,4-dioxane have been determined at 313.15 K and atmospheric pressure using an isothermal flow microcalorimeter and a digital vibrating density meter. Redlich-Kister polynomials were fitted to the experimental data, and smooth representations of the results are presented.