Using the simulation program of Kermode and Weaire, we have calculated stress‐strain curves for a number of samples of two‐dimensional foam, under extensional shear (planar extension). The elastic constant takes a value close to that of the ideal hexagonal foam (with the same mean cell area) for all the samples studied. Similarly the plastic behavior shows only slight variation among reasonable disordered structures. Stress increases monotonically with strain, with an asymptotic yield stress of the same order as the values calculated by Kermode and Weaire for the hexagonal structure. The stress‐strain relationship is therefore roughly represented by a hyperbolic tangent function.