iPhone: UIScrollView not scrolling when adding item via IB

I'm trying to make a very simple scrolling page via IB. What I've got is a UIImageView at the top and 2 UIImageViews at the bottom, with a UITextView in the middle. I've disabled the scrolling in the UITextView as I won't the whole page to scroll up and down including开发者_运维技巧 the UIImageViews.

Can anyone tell me why the UIScrollView won't scroll up and down? All of the items above are subviews of UIScrollView via IB.

You can only scroll in a UIScrollView if the contentSize is larger than the frame. Have you set this?