Filament wound glass fibre reinforced epoxy cylinders with thickness : internal diameter ratios of approximately 0.01, and winding angle ± 85° have been tested to failure under different combinations of axial load and internal pressure. The effect of the interaction coefficients in the Tsai—Wu failure criterion equation are considered. Results for the 17 specimens tested and published results for other winding angles have been used to assess some commonly used forms of failure criteria. It was shown that inclusion of the radial stress terms had no significant effect on the experimental results considered. The geometries and hoop to axial stress ratios for which radial stresses are likely to be important are stated.