Vapour extraction (VAPEX) is a potentially economic process for the recovery of heavy oil and bitumen in Canadian reservoirs, as all of the injected solvent is effectively delivered to the zone of interest. In addition, the process has the potential to sequester greenhouse gases, and is capable of in situ upgrading of heavy oil. The research described in this paper was undertaken to identify the main processes governing the interfacial mass transfer of solvent into bitumen. A number of experiments were carried out in a Hele-Shaw cell, and the results were incorporated into a predictive model, Good agreement between theory and experiment was found when dispersion effects were incorporated into a mass transfer model of the process at identical values of Peclet number.