A method of moulding superplastic alloy sheet material by holding a blank of sheet material, heated to a temperature at which it exhibits superplasticity, adjacent a fluid pressure duct or manifold, and applying fluid pressure to the blank sheet through the duct or manifold to cause the heated sheet to conform to the shape of a mould surface arranged on the side of the sheet remote from the duct or manifold. The fluid pressure manifold may be a heated plate having a plurality of apertures therein.