The aim was to develop a tool for the critical appraisal of epidemiological cross-sectional studies. Several recommendations or guidelines for assessing the strength of scientific evidence provided by observational studies were reviewed, like those from the Agency for Healthcare Research and Quality, the Scottish Intercollegiate Guidelines Group, the Osteba (Basque Office for Health Technology Assessment), and the STROBE Initiative. The tool has 27 items to assess: study question or objective, participants, comparability between groups, definition and measure of main variables; analysis and confusion, results, conclusions, external validity and applicability, and conflict of interest. This tool can be used to critically appraise research papers or to rate evidence during the elaboration of systematic reviews.