Abstract This paper provides a method of estimating the internal pressure required to cause plastic expansion of a uniform circular tube under internal pressure, when the ends of the tube are constrained. Both ‘simple support’ and ‘clamped’ conditions at the ends are considered. The method is based on work considerations. The results obtained are shown to agree reasonably well with experiment, the form of the deformation being predicted very accurately and the magnitude of the pressure required to cause failure with fair accuracy. With some additional trouble the method can be extended to cover the effect of work-hardening. It is shown that the end effect is small unless the tube is very short.