Use the following links in this order to search for available dissertations and masters theses (full text online, in our collections, for purchase in print or available for Interlibrary Loan).
With more than 2.4 million entries, the ProQuest Dissertations & Theses database is the most comprehensive collection of dissertations and theses in the world. UMI offers over 2 million titles for purchase in microfilm or paper formats. More than 930,000 are available in PDF format for immediate free download, and an average of 2,000 new PDFs are added to the database each week.
Since about 2000, US & Canadian universities have required most current or new dissertations to be submitted in electronic format. A few students may still submit in print format (if they entered their graduate program prior to the new requirement). Some authors may also restrict external access for a limited time, for example if patent issues are a concern. At UF, we're retrospectively digitizing print dissertations, but copyright requires we secure author permission (or that of the heirs). Before looking any further, check the Library catalog to see if we have the title of interest. See the UF Electronic Theses and Dissertations and the Finding Dissertations & Theses pages for further information.
For the US & Canada, ProQuest maintains a database of all dissertations and a few "selected" masters theses. This is considered a form of publication. For years a few exceptions existed, as may still be the case for older titles at a very few institutions (Harvard University, MIT and the University of Chicago were long time holdouts). UF faculty, staff and students may download full text of over 600,000 theses from ProQuest Dissertations & Theses: Full Text. Full text is available for approximately one third of the theses indexed in the database. Check WorldCat Dissertations if you don't find the title of interest there (includes better Masters thesis coverage than ProQuest). Also, the Center for Research Libraries maintains an archive of dissertations produced outside of the US & Canada, but it is not comprehensive.
If you haven't found the title of interest in these sources, the next step is to search the degree-granting institution's library catalog for circulating print copies. Universities maintain one official copy as an archival record of the institution; it can't be loaned via ILL or charged out. A circulating copy may be available, but these can be stolen, lost or damaged, etc. When they go missing, they're usually not replaced.
European institutions may maintain a copy of dissertations only in departmental or college libraries, rather than the institutional library. The same is often true of master's theses at US institutions. Sometimes these are treated as manuscripts, so they can only be copied with the authors (or the author's heirs' permission). In the worst cases, the only way to access some exceptionally difficult theses and dissertations is to travel to the originating institution and sign permission forms yourself.
Feel free to contact your library disciplinary specialist if you need assistance or have any further questions.