You can read about it here:
http://www.houseofboyd.com/blog/?page_id=106&forumaction=showposts&forum=3&thread=74&start=0

Took some legwork, but using your good directions and google maps, it seems to now be something called the "Ledgemont Technology Center" - strange you can search Jefferson Institute Coma all you want, and you can't find any pictures of how it now looks. But your guide helped ferret it out (I think..) - thanks!
I'm an artist! I have zest and appetite and I like food!

I spent some time driving around Lexington last summer and never found the place. Thanks for your help, I'll give it another shot!

You should post the information to the trivia-section. It looks better than the one in there. Anyway I live in Finland so it's hard to say but if I ever go there I probably try this newer version.

Did you ever find the Institute?

Many thanks. x

Its right off Rt 128 between Lexington and Waltham by Rt 2. They changed the angled windows a couple of years ago and are now glass fronted, but the building looks the same in the back pretty much. Get off at the Trapelo Rd exit, go left, then left onto Spring St (this is assuming your going South on 128)Youll see the entrance on the left, but you will be coming the opposite direction they did in the movie. Also, the main hospital building Susan walks into at the begining is gone-it was the original entrance to Boston City Hospital, and was torn down about 3 years ago to make room for the new hospital. The Holiday Inn she hides out in is visible on the right from 93 just before the new Storrow Drive exit. Hope this helps!