Excess molar enthalpies H-m(E) and excess molar volumes V-m(E) have been determined for (2-methylpropane + 2-methylpropene), (2-methylpropane + propan-2-ol), and (2-methylpropene +propan-2-ol) at the temperatures (298.15 and 323.15)K and at the pressures (5, 10, and 15) MPa. For (alkane + alkene), H-m(E) and V-m(E) are small and positive for all values of mole fraction I of alkane, with small temperature and pressure coefficients. For (alkane + alkanol) and (alkene + alkanol), the H-m(E) results and the excess molar heat capacity C-p,m(E) are large and positive, while V-m(E)(x) is s-shaped, changing from negative to positive with increasing mole fraction of the hydrocarbon. Pressure has a small effect on H-m(E) for these systems, but affects V-m(E) by decreasing the magnitudes of the positive and negative regions of the s-shaped curves and shifting the intersection with the abscissa (V-m(E) = 0) to lower mole fraction of the alkane or alkene with increasing pressure. Comparisons are made among the three systems of the effect of the hydroxyl group and the double bond on X(m)(E)(x) and V-m(E)(x). These systems are also compared with (n-alkane + n-alkanol) of similar molar masses.