I almost always use Amex for car rental, and have never had a problem with it being accepted. Of course I do almost all of my charging with my Amex anyway, so.... An added benefit is that you can waive the extra insurace the car rentla types will try to push, bcs in addition to you homeowners policy and your auto insurance policies at home covering you, you get additional coverage just by using your American Express card. Take a look at their site and click on car rental or some such thing. You will not regret it.