I don’t know of any other t-shirt company that awards a prize as big as this. Of course, the UT Grand Prix is not an ongoing t-shirt competition but rather an annual event that is being held for the 5th time this year. If I am reading the Japanese correctly there have been 60,750 submissions over the last 4 years of which 166 were produced as t-shirts. Below is some information from their site. I think there is more information to come regarding the design application process but as the design submissions don’t open until July 15th I would concentrate on planning your next best designs.

Prizes:

The Grand Prix will be awarded three million Japanese Yen (approximately $30,000 US/ ₤15,000GB). There will be other secondary awards as well and all winning designs will be merchandized globally in UNIQLO stores.

Application period

July 15, 2008 to September 21, 2008

Qualifications

There are none, anyone, anywhere in the world can apply.  (If you are under 18, and are selected as a finalist you must have parent/guardian approval)

Selection Committee

The UT Selection Committee is comprised of Mr. Kashiwa Sato (Art Director, Tokyo), Ms. Yayoi Kusama (Avant Garde artist) and 6 other industry professionals

Evaluation process

The UT Selection Committee will evaluate the T-shirt design submitted
Evaluation 1st Pass: We will announce the semi-finalists on the web at the end of October 2008.
Evaluation 2nd and final: We will announce the grand pix and secondary winners in Spring 2009.

Application process

Please see the UT website for a detailed explanation of the application procedure in contest.
http://ut.uniqlo.com/utgp