ing the error detection and correction/recovery performance of the system. This approach requires the use of an accelerating agent to produce sufficient faults to gather statistically valid measurements on the fault tolerant performance of the system. Fault and error injection have also proven effective in measuring the effectiveness of error detection and correction/recovery properties of fault tolerant systems. In addition to the ability to measure fault tolerance, the methods provide the capability to study the consequences to system operation presented by faults which escape detection or are not afforded complete correction or recovery. Two primary methods have been utilized to perform fault injection: simulation based methods and physical injection provisions. Simulation based methods provide the capability to establish the time of occurrence, location and type of fault, and the transient or permanent characteristics of the fault. Physical injection of faults utilizes charged particles, such as heavy- ion fission fragments from a Californium-252 source to produce single event faults. Most fault injection experiments performed to date were not designed around a formalized methodology. Experimenters typically developed customized approaches to validate each new system. This makes it difficult to apply the specific results from individual studies to the analysis of other systems. The complexity of present systems result in the need to perform many experiments to achieve statistical confidence in the characterization test. Several fault injection tools address the need for accelerated fault injection and measurement processes; Messaline, Fiat, Ferrari, Focus, Depend, and React are the ones most discussed in the literature. Validation and verification of system performance utilizes the results of physical and/or simulated fault injection experiments to assess the coverage of faults which produce undesired system response and the ability of detection and recovery provisions to assure proper system operation. These