In recognition of its responsibility to assist institutions in the interpretation and use of GRE scores in the graduate admissions process, the GRE Board established the GRE Validity Study Service (VSS) in 1979. The VSS can be a useful tool in determining how information about applicants (predictor variables) can be used to make judgments about the probability of their success in graduate school (criterion variables). The purpose of this report is twofold: 1) to describe the VSS and its participants and, 2) to summarize what we know about the validity of the GRE tests. The first part of this report summarizes the conclusions drawn from 606 validity studies that have been performed for graduate departments in the last five years and discusses the policy implications that might be useful in admissions decisions. The remainder of the report describes the service and the results from which these conclusions have been drawn.