The complete solution is obtained for the problem of plastic analysis of a clamped, circular plate subject to a uniformly distributed transverse pressure over a circular central region. The plate seals an incompressible perfect fluid; buoyancy effects are neglected. The plate material is assumed to obey the Tresca maximum shearing stress yield criterion; ignoring the effect of transverse shearing stress on the plastic behavior of the plate, the yield condition in terms of bending moments alone is taken to be the usual Tresca hexagon. The predicted limit pressure is compared with experimental results obtained from tests performed on mild steel and aluminum specimens. Good agreement between experiment and theory is obtained. The appearance of flow figures (L¨ders bands) on the steel plate surface is briefly described.