Molar excess volumes V E at 298.15 K have been determined as a function of mole fraction x for the two binary liquid systems oxane (tetrahydropyran, C 5H 10O) + cyclohexane( c-C 6H 12) and 1,4-dioxane(1,4-C 4H 8O 2) + cyclohexane by vibrating-tube densimetry. In addition, a Picker flow calorimeter was used to obtain molar excess heat capacities C P E at constant pressure at the same temperature. V E is positive for both systems and rather symmetric, with V E( x 1 = 0.5) amounting to 0.317 cm 3 mol −1 for &[; x 1(C 5H 10O)+ x 2( c-C 6H 12)&];, and to 0.961 cm 3 mol −1 for &[; x 1(1,4-C 4H 8O 2)+ x 2( c-C 6H 12)&];. For the former system, C P E is negative and noticeably skewed toward the cyclohexane side. The composition dependence of C P E for the latter system is rather unusual in that two minima are observed, the more pronounced being situated at x′ 1,min = 0.173, with C P E( x′ 1,min) = −0.97 J K −1 mol −1. The second minimum is rather shallow and is located at x″ 1,min = 0.761, with C P E( x″ 1,min) = −0.56 J K −1 mol −1. The maximum of the curve is at x 1,max = 0.539, with C P E( x 1,max) = −0.47 J K −1 mol −1.