You should generally use one view controller-per-nib file; it makes things much easier. A few things to check:

1. Is your view controller object being created (set a break point in its init, loadView, or viewDidLoad methods)
2. Is your view being displayed (set a breakpoint in your viewWillAppear: or viewDidAppear: methods)
3. Is your view properly hooked up (make sure the view outlet in IB is hooked up correctly; this is a common mistake)

You should generally use one view controller-per-nib file; it makes things much easier. A few things to check:

1. Is your view controller object being created (set a break point in its init, loadView, or viewDidLoad methods)
2. Is your view being displayed (set a breakpoint in your viewWillAppear: or viewDidAppear: methods)
3. Is your view properly hooked up (make sure the view outlet in IB is hooked up correctly; this is a common mistake)

If your question is actually how to load a nib file that's paired with a UIViewController subclass, take a look at UIViewController's -initWithNibName:bundle: and -loadView methods.