Ass-vertising is a new ad medium from a crazy advertising agency, NightAgency, which is based on a simple philosophy; "if you want to be seen, go where people are already looking". It involves putting a logo, a web address, or a brief message on the seat of a pair of bikini style panties. The panties are then worn by beautiful girls and ready to show your message to the target.

As shown part of a ass advertising campaign on the picture, bunch of shapely asses paraded outside Grand Central Station in New York to promote the New York Health and Racquet Club and a class they offer, called, appropriately, "Booty Call."