The design of light-gage steel corrugated shear diaphragms is not yet covered by the structural codes of many countries, including Canada. The shear capacity of steel diaphragms may be predicted by various approaches currently available, namely, those proposed by: (1) the American Iron and Steel Institute; (2) the Manual of seismic design of buildings, published by the U.S. Departments of the Army, Navy, and Air Force; and (3) the recommendations outlined in the current British code. In this paper, a rational method is proposed and the application of all the above methods is illustrated with reference to a specific example. Finally, the shear strengths of many diaphragms are predicted by the new approach developed by the authors and the results are compared to test data.