R Re el la at ti io on ns sh hi ip p b be et tw we ee en n p ph hy ys si ic ca al l a ac ct ti iv vi it ty y l le ev ve el l a an nd d d de em mo og gr ra ap ph hi ic c c ch ha ar ra ac ct te er ri is st ti ic cs s, , e ea at ti in ng g h ha ab bi it ts s a an nd d s se ed de en nt ta ar ry y b be eh ha av vi io or rs s o of f T Tu ur rk ki is sh h s sc ch ho oo ol l c ch hi il ld dr re en n a ag ge ed d 1 11 1, , 1 13 3 a an nd d 1 15 5 y ye ea ar rs s E Et th he em m E Er rg gi in nö öz z, , M Mü üj jg ga an n A Al li ik ka afl fli if fo o¤ ¤l lu u* *, , O Oy ya a E Er rc ca an n* *, , Ö Öm me er r U Uy ys sa al l* ** *, , B Ba ar r› ›fl fl E Ek ki ic ci i* O Or ri ig gi in na al l A Ar rt ti ic cl le e S Su um mm ma ar ry y Aim: The aim of this study was to determine the relationships between physical activity level and demographic characteristics, body mass index and some other health behaviors in Turkish adolescents. Material and Method:The data presented in this study were a part of the Turkish data collected for the cross-sectional and international "Health Behavior in School-aged Children 2005/2006 study" which aimed to evaluate adolescents' health and health behavior around Europe and North America. The data were collected from 3884 students aged 11 and 13 years (1946 males, 1938 females) who attended 180 classes of 82 primary schools in 26 cities and 1668 students aged 15 years (901 male, 767 female) who attended 88 classes of 83 high schools in 26 cities. Statistical analyses were made by using chi-square test, factor analysis and logistic regression analysis.Results: Twenty percent of the students reported that they were physically active for at least 60 minutes each day over the course of a week. In logistic regression analysis being 11 and 13 years old, being male, spending 4 or more evenings with friends outside the home were found to be associated with being physically active. When the "eating both healthy and unhealthy foods rarely" group was taken as the reference group, the other 3 groups (healthy foods frequently + unhealthy foods rarely; unhealthy foods frequently + healthy foods rarely; eating both healthy and unhealthy foods frequently) were more likely to be physically active than the reference group. Conclusions:The results of this study are important in terms of showing that physical inactivity is common among Turkish adolescents, especially in females. These results are also important in terms of showing that both eating habits and time spent with friends are related to physical activity of adolescents. Effective health promotion programmes should be especially focused on females and emphasize the importance of adolescents' eating habits. It should also be remembered that peers could play an important role in improving adolescents' physical activity level.