The online United Nations Treaty Collection is now free to all. At the Subscriber Log-In, enter the generic Username  <treaties> and generic Password  <12345>. If you forget, just look for the Note from the Treaty Section, Office of Legal Affairs at the  treaty collection website.

The online treaty collection has not been updated since November 2007, however. So,  consult the Journal of the United Nations for recent treaty signature and ratification information. The UN is reportedly in the process of redesigning its treaties website, but no word yet about when a new site will debut.

If you don't find the treaty that you need on the internet, Heafey Law Library does have the UN Treaty Series in microfiche and UN Treaty indexes and finding guides in print. Lexis,  Westlaw, and Hein Online all have treaty databases, but none has the entire UN Treaty Series.