The aim of this study was to determine the prevalence and the socioeconomic risk factors associated with obesity among female school-aged children and adolescents in primary and intermediate schools in Al-Khobar city, Kingdom of Saudi Arabia. This is a cross-sectional study conducted in Al-Khobar city, which is located in the eastern part of Saudi Arabia, during the period of January to March 2003. It involved 2239 female schoolchildren randomly selected from 30 regular government and private primary and preparatory schools. The students' ages ranged from 6 to 17 years, with a mean of 10.49 +/- 2.64 years. A multistage stratified random sampling technique with proportional allocation was used. Data were collected using questionnaires and anthropometric measurements. Body mass index interpretation was based on using a table of standard definitions for overweight and obesity in children (Cole's). The spss version 10 (SPSS Inc., Chicago, IL, USA) was used for data entry and analysis. A chi-squared test was used in cross-tabulation analysis to test the significance of association between body mass index and socioeconomic variables. The prevalence of overweight and obesity were 20% and 11%, respectively. The prevalence of overweight was higher among schoolchildren with father in private work (P<0.01) and the prevalence of overweight and obesity was higher among schoolchildren with highly educated mothers (P=0.008). The prevalence of overweight and obesity among female school-aged children and adolescents in the Al-Khobar city was very high. Accordingly, it is recommended that health education programmes regarding obesity should be provided to all schoolchildren, their families and teachers.