Is he neutered? If not have him neutered
asap!

There's a thread elsewhere on the board
about indoor/outdoor issues: http://PetoftheDay.com/talk/Forum13/HTML/000016.html

I'll also add: http://www.wenet.com/~amazon/happycat.html http://www.vospca.org/archive/indoorcat.html http://www.runway.net/b/moonmaid/in-or-out.html http://www.hdw-inc.com/leashtraining.HTM http://maxshouse.com/Healthy+Happy_Indoors.htm