In this paper, a newly developed dynamic pendant drop volume analysis (DPDVA) method is applied to measure the diffusion coefficients and oil swelling factors of four pure solvents (carbon dioxide, methane, ethane, and propane) and three solvent mixtures (mixture #1: 70 mole% carbon dioxide + 30 mole% propane, mixture #2: 70 mole% methane + 30 mole% propane, and mixture #3: 70 mole% ethane + 30 mole% propane) in Lloydminster heavy oil in the pressure range of 0.4-14.0 MPa and at T = 23.9 degrees C. The experimental results show that both the diffusion coefficient and the oil swelling factor of a heavy oil-solvent system increase with pressure. In particular, the diffusion coefficients and oil swelling factors of propane and ethane in heavy oil at pressures slightly lower than their respective vapour pressures are relatively large (D >= 0.680 x 10(-9) m(2)/s, f(sw) >= 1.314). It is also found that the apparent diffusion coefficients and the apparent oil swelling factors of the three solvent mixtures at pressures slightly below their respective dew-point pressures are large (D-a >= 0.706 x 10(-9) m(2)/s, f(sw) > 1.351). The experimental results clearly indicate that there exist certain correlations among the diffusion coefficient, oil swelling factor, solubility, and viscosity of a heavy oil-solvent system. Further experimental and theoretical studies are needed to determine these correlations. (c) 2006 Elsevier B.V. All rights reserved.