Experimental data for the diffusivity of carbon dioxide, methane, ethane and nitrogen in Athabasca bitumen are presented in the range 25-90degreesC at 4 and 8 MPa. The diffusivity of these gases has been determined as a function of gas concentration in bitumen using a non-intrusive experimental method. The diffusivity of gas in general is found to increase with temperature and pressure, and is a unimodal function of concentration. A correlation is provided for the average diffusivity of these gases as a function of temperature.