This Safety Guide provides recommendations on the safety assessment for research reactors in the authorization process, and on performance of safety analysis and preparation of the safety analysis report. It also incorporates the relevant lessons learned from the accident at the Fukushima Daiichi nuclear power plant and elaborates guidance on interfaces between nuclear safety and nuclear security. The recommendations in this Safety Guide are intended for operating organizations of research reactors; it can also be used by designers performing a safety assessment for a research reactor. Furthermore, this guide provides useful guidance for regulatory bodies performing a review and assessment of submitted safety analysis reports as an important document within authorization process. This Safety Guide is a revision of IAEA Safety Standards Series No. SSG-20, which it supersedes.