Debit and Cash. no credit cards.Costco is good if you have a friend or family member to share with. Accepts Otherwise, monstrous sizes may or may not be good for you! It's good that they have samples of things, because of course, who wants a years supply of something that's not their fave. The gasoline alone is worth the price of admission. Take advantage of their optical and pharmacy to really rack up the savings. if you do wear glasses, definitely pick up a set of cleaner, it's a crazy deal. $5 gets you two spray bottles of cleaner, two microfiber cloths, a keychain screwdriver, a mini bottle, and free refills. can't beat that. Unfortunately, they switched from high quality to kirkland hot dogs at the cafe, so I can't recommend them. however, the pizza is yummy for a quick bite on your way out with your haul.