Approximately 80% of the Canadian oil sands are too deep to be economically mined. SAGD, an in situ recovery technology, has come of age and is emerging as the technology of choice in exploitation of these resources. The current major challenge that SAGD faces is the use of expensive heat to generate steam. The authors have previously described an improvement to SAGD, Solvent Aided Process (SAP), that aims to combine the benefits of using steam with solvents. In SAP, a small amount of hydrocarbon solvent is introduced as an additive to the injected steam during SAGD, SAP holds the promise to significantly improve the energy efficiency of SAGD thus reducing the heat requirement. This paper describes field testing of SAP at EnCana's Christina Lake SAGD Project. In addition to dwelling on some of the important parameters of a SAP test, it outlines the design considerations for the pilot and associated facility modifications. The design duration of the experiment calls for an assessment of reservoir performance on a long-term basis. However, some preliminary observations and indications are discussed. Additionally, impact of timing of solvent initiation and the well pair spacing on process performance is also explored based on modelling exercises.