The mutual dependence of mass and momentum transport at fluid interfaces was studied theoretically and experimentally. Applying thermodynamics of irreversible processes to systems with interfaces showed on a theoretical basis, that the dilation of the interface acts as a thermodynamic driving force for the mass transfer across the interface. Mass-transfer rates and concentration profiles at the dilated interface between toluene and water were measured using holographic inteferometry for various transfer components. Experimental study showed that mass-transfer rates ina ease with increasing dilational rate, due solely to an enhanced convective transport in the continuous phases. The dilation does not affect the concentrations at the interface. It was demonstrated theoretically that the maximum possible alteration in the interfacial concentrations due to dilation was in the order of magnitude of rite experimental accuracy of the interferometer. it was concluded that the thermodynamic driving force due to dilation is - if present - too small to be relevant to technical applications.