Rating scales were developed for several factors that were considered relevant to the problem of clinically evaluating dental restorative materials. Examiners were trained to use the rating scales, and their performance was evaluated in field trials. Data analysis of examiner performance was used to revise the written criteria, and to train the examiners in making consistent judgments of dental restorations. Criteria were adopted when field testing indicated that examiners were able to duplicate their own judgments and judgments of other examiners at a predetermined level of acceptability. Further experience with the rating scales in actual clinical studies led to the consolidation of anterior and posterior criteria, which had been developed separately, and to the deletion of certain rating scales which failed to yield useful information. The rating scales which were finally adopted are for color match, cavo-survace marginal discoloration, anatomic form, marginal adaptation, and caries.