Background: Eustachian tube dysfunction and tuba aperta occurs when a patient has a problem with performing one or more of the primary functions of the Eustachian tube: Ventilation, clearance and middle ear sound protection. Recent research is primarily focused on treatment options, especially in obstruction of the Eustachian tube. Without clear diagnostic criteria, it is difficult to compare the results of these studies, as the inclusion criteria for the patient group differ between the studies. This thesis is a review of articles about tests of Eustachian tube function. Methods: Literature review of articles about Eustachian tube function tests. Search performed in PubMed in April 2016, 1229 abstracts were reviewed and 129 articles included in the thesis. All articles with a test of ET function and clear methodology were included, as well as review papers. Results: 129 articles on several types of tests were evaluated. The included papers had limitations. The methods were often either complicated or too simplified. Few authors list bias or test accuracy. The instruments described were not always commercially available. There are tests that can diagnose tuba aperta with a high level of sensitivity and specificity, but there currently exists no gold standard test in the diagnosis of Eustachian tube dysfunction. Promising new tools include the Eustachian tube dysfunction questionnaire (ETDQ-7) and the Eustachian tube score (ETS-7). Conclusion: There is no gold standard on diagnosing Eustachian tube dysfunction, but tuba aperta can in most cases be diagnosed with a simple test battery. In Eustachian tube dysfunction, several tests need to be combined to increase the accuracy of diagnosis until further research is conducted.