The clinical diagnosis of secondary caries is the main reason for replacement of all types of directly-placed restorations. This is an ill-defined clinical diagnosis both in teaching programs and in general practice. The criteria for the diagnosis must be improved and come in line with those for primary caries. Secondary caries are usually localized and delineated lesions and should be differentiated from stained and ditched margins. Small defects of secondary caries, stained and degraded margins may be removed by refurbishing/refinishing procedures. Larger defects may be explored by removing part of the restoration to access the defective margin. By removing part of the restoration to the full depth, a firm diagnosis can be made regarding the extent of the lesion, as the defects are often well delineated. Provided the main part of the restoration is satisfactory, the "exploratory" cavity preparation can then be filled with an appropriate material. These approaches will save tooth structure and be cost-effective. However, longevity data are lacking with such studies in progress.