For travel to Tibet, an entry permit issued by the Tibetan Tourist Bureau is required. You are supposed to contact a Chinese Tour Operator to organize an entry permit before applying for a Chinese visa. As far as I am concern, only travel agencies are entitled to apply for a Tibet Travel Permit. Individuals are not allowed to visit Tibet independently.

I would recommend that you go through a travel agent and let them take care of it for you. The Visa you have to take care of through the Chinese Consolute; however the special travel permit that gets you into Tibet is a little tricky. Be sure to get with a reputable travel agent. That's what I did and it worked out nicely without a hitch.