Background: The Chilean Ministry of Health has developed a health promotion program called «Vida Chile», whose aim is to target risk factors for chronic diseases. To achieve this, school-based initiatives in nutrition and physical activity have been implemented. The evaluation of these initiatives includes a baseline assessment of these two variables. Aim: Baseline assessment of the nutritional status and aerobic capacity of elementary school children (1st to 8th grade). Material and methods: Children from seven public schools were studied. Weight, height, triceps skinfold thickness and waist circumference were measured. To test the aerobic capacity, the 20-m Shuttle Run Test (Navette) was utilized. Results: The assessment included 4,271 children, mean age was 10.2 years. The percentile of body mass index, as compared to the CDC 2000 Reference was 67.8±26.7 and 68±26.7 for boys and girls, respectively. The prevalence of obesity among children from 6 to 8 years, was 20.3 and 17.7% for boys and girls, respectively. Approximately 30% of males and 15% of females with normal weight had a good aerobic resistance, compared to 15 and 4% of their overweight counterparts. Aerobic capacity decreased with increasing age. Conclusions: There is a high prevalence of obesity and a deficient level of aerobic capacity among children attending public schools in Chile