Fault tolerant design is receiving considerable attention at present in order to safeguard against improper operation of digital systems in critical applications. A number of multiprocessor systems featuring hardware fault tolerance are now available commercially. The paper presents an overview of some of the work done so far in the application of fault tolerance techniques to improve the reliability and availability of microprocessor-based systems. An alternative approach to enhance the reliability of a system is to apply self-checking techniques, primarily through the use of error detecting codes. By merging the fault tolerance and the self-checking techniques, the reliability and the maintainability of microprocessor-based systems can be significantly improved.