Reliable Digit Span (RDS) is a heavily researched symptom validity test with a recent literature review yielding more than 20 studies ranging in dates from 1994 to 2011. Unfortunately, limitations within some of the research minimize clinical generalizability. This systematic review and cross-validation study was conducted to address these limitations, thus increasing the measure's clinical utility. Sensitivity and specificity rates were calculated for the [less than or equal to]6 and [less than or equal to]7 cutoffs when data were globally combined and divided by clinical groups. The cross-validation of specific diagnostic groups was consistent with the data reported in the literature. Overall, caution should be used when utilizing the [less than or equal to]7 cutoff in all clinical groups and when utilizing the [less than or equal to]6 cutoff in the following groups: cerebrovascular accident, severe memory disorders, mental retardation, borderline intellectual functioning, and English as a second language. Additional limitations and cautions are provided. (Contains 5 tables.)