The concentration dependence of diffusion coefficients for methyl oleate (MO) and anhydrous milk fat (AMF) in supercritical carbon dioxide (SC-CO2) at 40 degrees C and various pressures was measured in these two-phase systems by a steady-state method. The applicability of Schreiner＇s type equations, which are based on the chemical potential driving force, was evaluated for these systems. The thermodynamic factor for each solute was determined from the Peng-Robinson equation of state. For MO, Schreiner＇s type equations represented its diffusion adequately. The equations with viscosity correction were better than those without it. However, this approach was not successful for the AMF/SC-CO2 system when AMF was considered as a pseudopure component.