The paper discusses a data attribute rating system (DARS), developed by EPA to assist in evaluating data associated with emission inventories. he paper presents DARS for evaluation by the potential user community. ARS was originally conceived as a method for evaluating country-specific inventories of greenhouse gases. owever, it has been broadened to cover a wider range of emission inventory types. he system disaggregates emission inventories into emission factors and activity data, then assigns a numerical score to each of the two components. ach score is based on what is known about the factor and activity parameters; e.g., the specificity to the source category, the spatial (geographic) congruity, the measurement; or estimation techniques involved, and the temporal congruity. he resulting emission factor and activity data scores are combined to produce an overall confidence rating for the inventory. everal methods of combining the values are discussed and compared. lthough numerical values are generated, the system is only semi-quantitative. owever, DARS should be useful in providing more information about inventories than the usual qualitative grading procedures used to characterize data. he individual rating components are presented, and the attribute evaluation techniques are discussed. xamples of applications are also discussed.