The steam-assisted gravity drainage (SAGD) process has been demonstrated to be commercially viable for the recovery of bitumen from the Athabasca Oil Sands region. One of the potential long-term concerns with the process is the relatively high use of energy. The majority of the projects underway have steam-oil ratios (SOR's) in the range of 2.5 to 3.5. This translates into combustion of approximately 20 - 28% of the energy contained in the oil produced. To reduce the current level of energy consumption, many Studies have investigated the addition of solvents to the steam. A small number of field trials have been conducted, with apparently encouraging results. The use of hexane, or a similar commercial grade naphtha mixture, as a solvent appears promising, as it would closely match the vapour pressure curve of steam and would tend to flow and condense with the steam. This study presents the results of numerical investigations regarding the implications of the addition of hexane to steam with respect to the design of SAGD solvent injection wells. This study found that the SOR at full depletion of a steam-hexane SAGD, in the absence of a wind-down strategy, would be improved over that for conventional SAGD only by the degree that heat losses to the over- and underburden are reduced due to more rapid bitumen production rates. At short and intermediate times, a more significant SOR improvement will result primarily from the more efficient drainage of bitumen from the chamber walls and floor, reducing the thickness of the heated formation that is undrained. It was also concluded that injection wells for steam-hexane SAGD will require the same diameter wellbores as for conventional SAGD injection wells. Existing SAGD injection wells can be directly converted to steam-hexane use as overall project economics dictate.