I called America PRICELINE EXPRESS about this today, since I previously signed up for the premium rental car insurance which is effective (at $24.95 a pop) whenever the computer see a charge from Hertz, Budget, etc. This insurance is primary. I asked whether their system will recognize a Priceline rental as qualifying under the insurance policy. Their answer was that Priceline rentals do qualify but that the documentation needs to be generated manually by the Amex insurance office. They requested that I notify them in advance, giving the rental date, location and whatever, so that they can log in the coverage. While the phone number on the back of the Amex card will work, it is faster to call the insurance office directly, 1-800-338-1670.