[en] This paper describes a study performed at the University of Waterloo which combined data from nine investigations of fatigue of mild steels at room temperature under fully-reversed, biaxial, stress or strain controlled, conditions. This assemblage of some 260 data points covers the fatigue life range from 10 to 10⁷ cycles. Biaxial stress ratios, from equibiaxial (+1) to torsional (-1) are represented. By combining data a broad view of the effect of biaxiality on fatigue is obtained. Areas where data are scant or show inconsistencies become apparent and conclusions drawn have more general applicability than those based on a single investigation. The data analyzed are published as amplitude or range of stress, total strain, plastic strain or equivalent plastic strain. A variety of testing techniques and interpretations of specimen failure were used. The chemical composition and heat treatment of the steels used also varied. The paper shows how some standard and other less usual strain based criteria describe the data. Two-part criteria were investigated in which the equivalent elastic and plastic strain components are based on either octahedral - or maximum -shear strain with the equivalent plastic strain modified to include a hydrostatic stress effect. The collected data were also compared to the ASME Pressure Vessel Code curves for design against fatigue. The safety factors included are shown to be less than the desired 2 on stress or 20 on life particularly at short fatigue lives. Some modifications to the design practice to restore these safety factors are suggested