Summary.One hundred and eight children from 11 to 14 years were given instruction on shears and rotations, and how these transformations could be used to show the truth of Pythagoras's Theorem. The experimental group, which saw a computer‐presented animated display of the transformations, scored more highly on a subsequent test than either of two control groups, the first of which saw no computer at all, but only a diagram sheet which was in the possession of all the children. The second control group saw a computer‐presented display which showed only the same ten discrete stages of the transformations as the diagram sheet. It was concluded that animation per se can facilitate the understanding of a mathematical t