Aims: To use a range of evaluation instruments to assess the content and quality of websites about temporomandibular disorders (TMD) and thereby provide guidance regarding the actual accuracy and comprehensiveness of the information of the sites. Methods: Sixty-seven websites resulting from an Internet search with the word "TMD" were evaluated using Journal of the American Medical Association (JAMA), DISCERN, and Health on the Net (HON) criteria, along with an evaluation method to assess the scientific quality of the website contents. Results were compared according to reviewer, website type, and presence of HON seal. One-way analysis of variance (ANOVA), Student t test, chi-square test, and Pearson correlation analysis were used as appropriate. Results: The mean content, HON, and DISCERN scores were 38.9%, below 50%, and 53.9% of the maximum possible score, respectively. Fewer than 50% of the sites displayed the author or reference of the information according to the JAMA benchmarks criteria. Every evaluation criteria showed good agreement among reviewers. Commercial websites were the most common, while sites of nonprofit organizations showed the highest content scores. The overall quality was poor to moderate for all website types. Conclusion: Sites concerning TMD were poorly organized and maintained. Also, most sites contained insufficient or scientifically incorrect information that could have a negative effect on the treatment outcome and prognosis of TMD. Clinicians should guide patients to reputable sources of information that will enhance patient comprehension and better treatment outcomes. Keywords: content, evaluation criteria, Internet, quality, TMD