The study was conducted to analyze the patterns of growth in height and weight and the prevalence of over-weight among Qatari school children aged 6-18 years. Weights and heights of a cross-sectional sample of Qatari school children were measured. These children were selected randomly, in equal proportions of age and gender, from different schools from urban and semi-urban districts. Appropriate statistical procedures were performed to produce smooth percentile curves for boys and girls using a two-stage approach. Initial curve smoothing for selected major percentiles was accomplished by various paramet-ric and non-parametric procedures. In the second stage, a normalization procedure was used for creating z-scores that closely matched the smooth percentile curves. The height and weight results were compared with the international reference values of National Center for Health Statistics/Centers for Disease Control and Prevention (NCHS/CDC). The prevalence of over-weight was calculated using the new International Obesity Task Force (IOTF) reference. Of 7,442 Qatari children studied, 50.3% were male and 49.7% female. The mean values for height, weight, and body mass index (BMI) increased with the age for both boys and girls until the age of 18 years, except BMI, which stabilized at the age of 16-18 years at around 22.6 for boys and at 21.6 for girls. The growth patterns of the Qatari children, aged 6-18 years, appeared to be comparable with those of the NCHS/CDC reference. The weight-for-age centile curves of the Qatari boys tended to be superior to those of the NCHS/CDC reference until the age of 15 years, less so those of the Qatari girls. In contrast, the height-for-age centile curves of the Qatari children tended to deviate in a negative sense from the NCHS/CDC reference curves, for boys and girls from age around 11 years and 13 years respectively. The deviation of the smoothed median height-for-age curves from the reference in adolescence could most likely be attributed to a later maturation among the Qatari children. The prevalence of under-weight, over-weight, and obesity for the Qatari children was quite below the CDC and IOTF rates, except for girls aged 6-9 years. More males than females were over-weight or obese according to either the local, the CDC, or the IOTF reference, and the prevalence increased with age. A good percentage of the Qatari children was at risk of being over-weight, which needs more attention because the development of obesity results in different types of diseases associated with changes in body composition.