This text is about methods used for the computer simulation of analog systems. It concentrates on electronic applications, but many of the methods are applicable to other engineering problems as well. This revised edition (1st, 1983) encompasses recent theoretical developments and program-writing tips for computer-aided design. About 60% of the text is suitable for a senior-level course in circuit theory. The whole text is suitable for graduate courses or as a reference for scientists and engineers who seek information in the field.