For several years, computer simulations of the development process of resists, patterned using optical or electron-beam radiation, have been confined to patterns consisting of long parallel lines. The simulation takes place in a section perpendicular to the direction of the resist lines; therefore, the simulation algorithms are called two dimensional(2D). The two-dimensional algorithms cannot be used to simulate the development of more complex patterns. For the first time, using a computer program recently created by the authors, the time evolution of the profiles of three complicated patterns, electron-beam exposed in PMMA (poly(methylmethacrylate) and developed in 1: 1 Methyl iso-Butyl Ketone/Isopropanol, is simulated in three dimensions(3D). We find the qualitative and quantitative predictions of the three-dimensional simulations to be in good agreement with experimental observations. The development of a 1.0μm contact hole is simulated using the 2D and 3D developer algorithms. A comparison of the results clearly point out one of the important but inherent limitations of all 2D developer algorithms. Copyright © 1981 by The Institute of Electrical and Electronics Engineers, Inc.