Medical research is a fundamental tool to achieve the advancement of science, through the improvement of strategies aimed to protect, promote and restore an individual's and society's health. Three characteristics are required to obtain approval of the research proposal: scientific relevance, technical quality and the accomplishment of ethical issues. The present review aimed at the determination of the specific criteria to perform a critical review of research proposals. A research was carried out in the PubMed, Medline, Ovid and Google Scholar databases, using the terms: peer review, research proposals, review and protocols, and reviewers. A total of 3546 related articles were reviewed, without finding a guide to critically assess research proposals. The guides to assess research articles consider that the quality criteria of the study should have been present since the study's conception; many of the issues described to review articles are incorporated in the review of the research proposals. The specific criteria were integrated to allow the reviewer to critically assess research proposals of different areas with scientific basis. The reviewer of research proposals should be considered as a professional that contributes to the promotion of knowledge advancement through his/her comments, which allow researchers to improve the quality of research proposals.