Abstract Objective To create a comprehensive evaluation of checklists and scales used to evaluate observational studies that examine incidence or prevalence and risk factors for diseases. Study Design We did a literature search of several databases to abstract format, content, development, and validation of the tools. Results We identified 46 scales and 51 checklists. Forty-seven of these tools were created for therapeutic studies, 48 for risk factors, and 5 for incidence studies. Forty-seven percent were modifications of previously published peer-reviewed appraisals, 18% were developed based on methodological standards, and 35% did not report development. Twenty-two percent reported reliability and 10% the validation procedure. Tools did not discriminate poor reporting vs. methodological quality of studies or external vs. internal validity; 35% categorize quality by the presence of predefined major flaws in design or by total score from the scale. Level of evidence was proposed in 22% of the tools by criteria of causality or internal validity of the studies. Evaluation required different degrees of subjectivity. Conclusions Format, length, and content varied substantially across available checklists and scales. Development, validation, and reliability were not consistently reported. Transparent objective quality assessments should be developed in the future.