Experimental information on the mechanism of yield and the associated strains is presented for mild-steel cylinders (2:1 diameter ratio) overstrained by internal fluid pressure. A limited number of Lueders’ lines develop and propagate through the cylinder wall according to distinct patterns. The strains vary circumferentially in keeping with the nonhomogeneous mechanism of yield. Comparison with homogeneous plasticity theories shows good agreement for circumferential strains provided a correction is made for the material yield stress. Axial strains are essentially elastic. Creep under maintained constant load is discussed in relation to strain and Lueders’ line movement.