This tutorial gives an overview of Software Quality Assurance (SQA) as applied to Computer Aided Design (CAD) systems. Basic concepts of SQA are discussed, and some of the theoretical background and current state of the art are presented. A pragmatic approach to SQA in the CAD world is demonstrated by showing its application to a VLSI layout editor. Some of the topics discussed are: reliability, robustness, verification and regression testing, test strategies and generation of test data, software change control, and how to handle some of the problems encountered when many people work on the same program.