Introduction : One of the recommended ways in organizing the information in the websites is the application of Meta Tags. The application of a variety of Meta Tags can affect the precision rate of search engines retrieval. They can also promote the rank of a website. The purpose of the study was to investigate the structure of libraries websites based on Meta Tags in medical science universities in Iran.

  Methods : This descriptive survey was carried out on 31 websites that included 342 web pages. Data was collected by a checklist and analyzed by SPSS.

  Results : Title meta tags (98.53%) and Charset meta tags (89.47%) among 15 meta tag types had the most usage and refresh meta tag had the least usage. Usage of keyword and descriptive meta tags were 55.6% and 55.2%, respectively. Generally, 100% websites under investigation used one type of meta tags.

  Conclusion : Title, Charest, Robot, Keyword and Descriptive meta tags received more attention from the designers of central libraries. But Googlebot, Refresh, Expire and cache Meta Tags received less attention. Librarians’ participation in creating library websites and the application of meta tags will play important role in electronic information retrieval.