OBJECTIVE: To determine the validity of Medline searches for randomised controlled trials in dental research (RCT-Ds), using the medical subject headings (MeSH-terms). DESIGN: The Medline database was searched for randomised controlled trials in dental research (RCT-Ds) published in 1999 and with MeSH-terms corresponding to different areas of dental research. All RCT-Ds were manually examined for relevance to the different areas of dental research and cross-tabulated against the Medline search results. The sensitivity, specificity, positive (precision) and negative predictive values, as well as the accuracy of the search results were calculated. RESULTS: The highest validity in the Medline searches for RCT-Ds was seen for endodontics, followed by orthodontics, whereas the lowest validity was seen for pediatric dentistry and public health dentistry. For pediatric dentistry the MeSH-term searches had too low a sensitivity for adequate location of RCT-Ds. CONCLUSIONS: MeSH-term searches on Medline are a useful tool for rapid location of RCT-Ds in most areas of dental research. However, there is a vast variation in the search validity. More refined search strategies are required to locate RCT-Ds in areas of dental research with low search validity.