It is shown that under certain conditions the grillage analysis of slabs can give incorrect results, so that the use of finite element analysis is to be preferred. Grillage analysis was applied to three slabs: a square plate simply supported on four sides; a rectangular plate simply supported on two sides; and a skew plate simply supported on two sides. The results were compared with those obtained using a finite element software package ( LUSAS ), and where available, with theoretical solutions. In certain cases the grillage results exhibit significant errors, and the situation was not improved by a local refinement. It was concluded that the use of finite element analysis is to be preferred, and that the use of the grillage method should be avoided. 7 refs.