AbstractIn designing a complex circuit, designers make a large number of circuit simulations, design changes and optimizations and can predict the circuit's performance reasonably accurately before committing it to silicon. It would be unthinkable to bypass detailed circuit simulation and optimization and rely on simple design rules and the testing of finished IC's to discover errors or to find out if the performance of the circuit meet specifications. Yet, this is basically the way IC reliability is treated today. A logical alternative is to predict circuit reliability at the circuit design stage through reliability simulation.Reliability simulator BERT is used to illustrate the physical models and approaches used to simulate the hot electron effect, oxide time-dependent breakdown, electromigration, bipolar transistor gain degradation, and radiation effects. The goal is to make circuit reliability simulation a part of the IC design process.