Despite evidence of increasing waterpipe tobacco smoking prevalence among U.S. young adults, little is known about the knowledge, attitudes, beliefs, and smoking patterns of waterpipe users in this population. To address this lack of knowledge, two convenience samples of U.S. waterpipe users were surveyed--one from a Richmond, Virginia, waterpipe café (n=101), the other from an Internet forum called HookahForum.com (n=100). Sixty percent reported first-time waterpipe use at or before age 18. Daily waterpipe use was reported by 19%, weekly use by 41%, and monthly use by 29%. Waterpipe use was more common during the weekend (75%) than during weekdays (43%). Forty-four percent reported spending >or=60 min smoking tobacco during a waterpipe session. The majority of waterpipe users owned a waterpipe (57%) and purchased it on the Internet (71%). Many waterpipe users smoked the sweetened and flavored tobacco (i.e., maassel), and fruit flavors were the most popular (54%). Past month use of cigarettes, tobacco products other than cigarettes or waterpipe, and alcohol was 54%, 33%, and 80% respectively, and 36% reported past-month marijuana use. Most waterpipe users were confident about their ability to quit (96%), but only a minority (32%) intended to quit. Most waterpipe users believed waterpipe tobacco smoking was less harmful and addictive than cigarettes. These results are from small convenience samples; more detailed study of a larger group of randomly sampled U.S. waterpipe tobacco smokers will be valuable in understanding this behavior and developing effective strategies to prevent it.