This systematic review evaluates evidence describing histologically validated performance of methods for identifying carious lesions. A search identified 1,407 articles, of which 39 were included that described 126 assessment of visual, visual/tactile, radiographic (film and digital), fiber optic transillumination, electrical conductance, and laser fluorescence methods. A subsequent update added four studies contributing 10 assessments. The strength of the evidence was judged to be poor for all applications, signifying that the available information is insufficient to support generalizable estimates of the sensitivity and specificity of any given application of a diagnostic method. The literature is problematic with respect to complete reporting of methods, variations in histological validation methods, the small number of in vivo studies, selection of teeth, small numbers of examiners, and other factors threatening both internal and external validity. Future research must address these problems as well as expand the range of assessments to include primary teeth and root surfaces.