Overweight and obesity are among the most prevalent nutritional problems in developed and developing countries. In this descriptive study, we attempted to determine the prevalence of overweight and obesity in Iranian adolescent girls attending high school in Tabriz. A sample of 1,650 (final study group, 1,518) high-school girls aged 14 to 20 years was selected by stepwise random sampling from five districts of Tabriz. Overweight and obesity were defined according to body mass index (BMI) percentiles from the First National Health and Nutrition Examination Survey (NHANES I) and the International Obesity Task Force (IOTF) BMI cutoffs. According to the NHANES I criteria, 14.6% of the study subjects were overweight or obese. Overweight and obesity was seen in 11. 1% and 3.6% of the students, respectively. By the IOTF cutoffs, 14% of the subjects were overweight or obese. Overweight and obesity were seen in 10.1% and 3.9% of the students, respectively. Of the study subjects, 8% had a BMI below the 15th percentile of NHANES I, an indicator of underweight. The prevalence of overweight and obesity in Tabriz high-school girls is higher than in many, but not all, parts of Iran, but lower than in some neighboring countries such as Saudi Arabia. In this age group, in addition to overweight and obesity, underweight (BMI < or = 15th percentile) is also present.