An experimental study was conducted to evaluate the effectiveness of the various components of Athabasca bitumen in stabilizing water-in-diluted-bitumen emulsions. The solvent used to dilute the very viscous bitumen was a mixture of 50:50 by volume of hexane and toluene. The various bitumen components studied were asphaltenes, deasphalted bitumen, and fine solids. It was found that asphaltenes and fine solids were the main stabilizers of the water-in-diluted-bitumen emulsions. Individually, the two components can stabilize water-in-diluted-bitumen emulsions. However, when both are present the capacity of the diluted bitumen to stabilize water emulsions is greatest. Emulsion stabilization tests indicated that whole bitumen had less capacity to stabilize water emulsions than asphaltenes and solids. This would indicate that the presence of the small molecules within the whole bitumen tends to lower the emulsion stability. Deasphalted bitumen acts as a poor emulsion stabilizer. Although deasphalted bitumen led to the least emulsion stabilization capacity, interfacial tension measurements showed that diluted deasphalted bitumen gave a greater decrease in the interfacial tension of water with diluent. Copyright 1999 Academic Press.