Assessing the prevalence of weight loss attempts in Beirut, Lebanon, a country characterized by a diversity of ethnic and religious groups and examining the interplay between ethnicity, body mass index (BMI) and weight perception and their relationship to weight loss behavior. A school-based survey of risk behaviors conducted among secondary students (grade 10-12) in 1997. Subjects consisted of 827 boys and girls, aged 15 to 23 years, the majority of whom were Moslems (65.4%). Multiple logistic regression was used to estimate the association between ethnicity and weight perception with the likelihood of trying to lose weight controlling for BMI and a number of potential covariates. The prevalence of weight loss attempts was 19.1% and 42.6% in boys and girls respectively. Christians were more likely to perceive themselves as overweight and to attempt weight loss than Moslems across all BMI levels, however this trend was significant in the underweight category. While controlling for BMI did not change appreciably the results observed, after controlling for weight perception, ethnic differences in weight-loss behavior disappeared. Findings of the study suggest that whereas actual weight may constitute only partially the driving force for differentials by ethnicity, the perception of body weight acts as a mediating factor in the relationship between ethnicity and weight loss behavior. Understanding the disparities in weight management behavior across various adolescent groups is key to develop culturally appropriate educational and intervention programs for the youths.