To go between the US and Canada you don't need a title at the border crossings.

However, to go to Mexico, Belize, Guatemala, El Salvador, Costa Rica,
Nicaragua, Honduras, & Panama you usually need a title (or proof of
registration if your state/province doesn't have a title).

People have been turned away at these borders for not having the
vehicle title in their car.  Better bring it just to be safe if you
go south....

>Why would they ask for the vehicle title at a border crossing, or
>why are you giving it to them?
>The title to my car sits in a safe-deposit box all the time.  You
>wouldn't want to have it in the
>vehicle.
>I've never had them even ask for the vehicle registration card at
>the Canada border.
>-Hans