The What Works Clearinghouse (WWC) Procedures and Standards Handbook (version 3.0) provides reviewers with a detailed description of the pilot single-case design standards and procedures. The WWC worked with single-case design experts to develop these pilot single-case design standards, as well as additional criteria for determining the rating of effectiveness for an intervention. These single-case design experts also helped the WWC develop Reviewer Guidance for Use with the Procedures and Standards Handbook, which clarifies how the pilot single-case design standards should be implemented in situations where the current Handbook is not sufficiently specific. This document summarizes the key criteria that are used when reviewing single-case design research and describes the process that was used to develop these criteria.