Deformation of some specimens produced by a stereolithography system was studied experimentally and numerically. Three steps in the rapid prototyping process, part building, part removal, and postcure, imposed significant effects on dimensional accuracy. Dimensions of the specimens were measured after each step. Distortion during part building was much smaller than that caused by the part removal step. The internal residual stress developed during building process was partially released by the removal of the part from the platform. Considerable distortion was also observed after postcure. A finite element computer code was developed to predict the deformation after each step. Shrinkage of each layer cured by the laser beam was simulated by considering thermal shrinkage of a solid layer. In order to simulate shrinkage during postcure process, it was assumed that the postcure occurred from the exterior surface to the interior surface. Heat sink was also assumed on the boundary of the part for the thermal stress analysis. Numerical results were consistent with experimental results for the simple geometry employed in this study.