Akl et al. BMC Public Health 2011, 11:244 http://www.biomedcentral.com/1471-2458/11/244 Page 8 of 12 Figure 4 Waterpipe use among university students. Adults 1 study conducted on US Air Force personnel reported a prevalence of 0.3% waterpipe smoking during their participation in a one year clinical trial of smoking pre- vention/cessation (Additional file 3; Part 3) [51]. European region School students A study conducted in a nationally representative sample of 11-15 year old school students in Estonia reported 21% current waterpipe smoking (Additional file 3; Part 4) [52]. The prevalence of current waterpipe smoking was about 1.5 times that of current cigarette smoking. University students A study on university students reported 38% ever water- pipe smoking, 8% regular waterpipe smoking and 5% waterpipe only smoking (Additional file 3; Part 4) [12]. Ever waterpipe smoking was associated with male gen- der, and cigarette smoking. Australia Adults A study conducted on Arabic speaking adults reported 11% current waterpipe smoking (Additional file 3; Part 5) [13,53]. Waterpipe use was associated with age group 40-59 (relative to >60), and other forms of smoking. Discussion In summary, surveys found alarming prevalence of cur- rent waterpipe smoking among school students in the United States, especially among Arab Americans (12%- 15%), [11,46-48] the Arabic Gulf region (9%-16%), [19-21] Estonia (21%), [52] and Lebanon (25%) [16-18]. Similarly, the prevalence of current waterpipe smoking among university students was high in the Arabic Gulf region (6%), [25] the United Kingdom (8%), [12] the United States (10%), [50] Syria (15%), [9,26-28] Lebanon (28%), [22] and Pakistan (33%) [42]. The prevalence of current waterpipe smoking among adults was the fol- lowing: Pakistan (6%), [45] Arabic Gulf region (4%-12%), [19,35,36] Australia (11% in Arab speaking adults), [13,53] Syria (9%-12%), [37,38] and Lebanon (15%) [33]. Studies reported high prevalence of group waterpipe smoking in Lebanon (5%), [33] and Egypt (11%-15%) [30,31]. In Lebanon, 5%-6% pregnant women reported smoking waterpipe during pregnancy [40,41]. Our findings are consistent with national surveys con- ducted by the WHO and the Global Youth Tobacco