Neil Mann Apr 15, 2010:

If it is one body, however many branches or offices it may have, it will use "the"; if you are dealing with a group of institutes then the rules about "the" in plural usages apply:
Institutes involved with medical ethics... (some, not necessarily all)
The institutes involved with medical ethics... (implies all)

As noted below, brief headlines or letterheads may omit the article, as also uses with initials, but text includes "the".

Adjectival use does not require the article:
The Goethe Institute's language courses are widely respected.
but Goethe Institute language courses are widely respected.

TTilch (asker) Apr 15, 2010:

also true when referring to several institutes? Would you also use it with article when referring to numerous institutes all over the world or only when you refer to a particular institute in a particular city?