THE MATCHING CASE METHODOLOGY is a technique for assigning effectiveness values to existing restraint systems.The importance of the matching case methodology is that it utilizes field accident data exclusively - accidents in which a specific restraint was used are compared to accidents of similar injury potential but whose occupants did not use the restraint being evaluated. The resulting average injury values enable the researcher to calculate that restraint system's effectiveness across the various classifications of injury severity. Because the methodology does rely upon accident data, projections of restraint system effectiveness have the potential to come much closer to reality than would be the case if they were dependent primarily upon the theoretical application of laboratory results.Although a portion of the methodology does involve some degree of subjective analysis, close control over the techniques used to implement the methodology should ensure relatively consistent results among any objective groups of trained researchers utilizing similar data banks for analysis.Thus far, the matching case methodology has been applied by General Motors to an early evaluation of the air cushion passive restraint. The following discussion will provide the results of this evaluation, but of more importance, will describe what is needed to conduct the methodology. The process by which air cushion effectiveness is calculated will also be described.