Because childhood obesity is still a growing problem in the world, we conducted this study aiming to show the trend in obesity (OB) and overweight (OW) prevalence in the last decade, to observe the alteration of OB and OW prevalence according to age groups and to construct the new age and gender specific body mass index (BMI) reference percentile charts for Turkish children living in the city center of Antalya. u n c o r r e c t e d p r o o f Methods: This cross-sectional study includes 1687 school aged children. International Obesity Task Force (IOTF) references were used to determine the obesity and overweight prevalence. OW was defined as BMI between 85 th and 95 th percentile, and OB above the 95 th percentile. The data obtained were compared with another study carried out by the same unit in the same region in 2003. LMS method, which summarizes terms of three smooth age specific curves called L (lambda), M (mu), and S (sigma), was used to construct the BMI reference percentile charts for Turkish children living in Antalya. Results: The prevalence of OB was 9.8 %, OW was 23.2 % and combined OW/OB was 33 %. Obesity prevalence was higher in boys than girls (p<0.05). The prevalence of combined OW/OB was highest at the age of 9-10 years. The prevalence of obesity has increased 2.9 times during twelve years in Antalya, Turkey. Conclusion: Comparing with the findings of previous decade, childhood obesity in Antalya has reached alarming level. Urgent measures should be taken to prevent obesity and more surveillance studies should be planned to show the future trend of obesity prevalence. What is already known on this topic? Increase in the frequency of obesity and overweight among children and adolescents is a major public health problem all over the world in both developed and developing countries. What this study adds? This is a 12-year interval study of our previous study conducted in 2006. Our findings suggest that OW and OB prevalence in the school-age children living in the same geographical region of Turkey have increased dramatically.