Category url structure

I am using wordpress3.0. In our site I want the url structure of the main caregoryies like http://www.oursite.com/cetegory2/, Where cetrgory2 is a category. But in Permalink Settings if I place /%category%/ in the Custom Structure the url become like http://www.oursite.com/category/cetegory2/. I wonder how to make the url stucture like http://www.oursite.com/cetegory2/.