The production of hydrogen sulphide and carbon dioxide is a feature common to all SAGD projects. Both gases are formed by a chemical reaction of steam condensate with bitumen in the SAGD steam zone in Athabasca; they are not normally present as solution gases. The production rates of these gases are therefore strongly dependent on operating characteristics of individual projects, primarily the steam pressure. The potential need for sulphur recovery plants in the larger SAGD project expansions creates the need for first order predictions of H2S production rates, so that appropriate sulphur recovery technologies can be identified. A simple method for the prediction of hydrogen sulphide production has been derived, such that, for most Athabasca projects in the 180 to 240 degrees C range of steam zone temperatures, a probable production rate estimate can be read off a simple graph. The graph is built from laboratory data on aquathermolysis, first provided by Hyne, and the assumption of pseudo-zero order kinetics of the aquathermolysis reaction that generates hydrogen sulphide. A temperature dependency is predicted, and is confirmed by field measurements of projects in the 180 to 240 degrees C range.