It is HUGE, but half of the inside is "stairs." The actual potty area is verrrrrry small. I would say only a very small cat would be comfortable using it.
This box gets very little use in our home. I thought maybe it was the location, so I moved it to another location in our home...a few times. No change. I scoop a potty out of it maybe once every 3 days.
http://www.petsmart.com/product/index.jsp?productId=4017038
