Objective: To evaluate the prevalence of overweight and obesity in a sample of Spanish schoolchildren by gender. Material and methods: The study involved 505 schoolchildren (259 boys and 246 girls), aged between 8 and 13 years (4th, 5th and 6th grade) from various Spanish provinces: A Coruna, Barcelona, Madrid, Seville and Valencia. Health, socioeconomic, anthropometric data (weight and height) and physical activity were collected and body mass index was calculated. Results: The prevalence of overweight was 15,9%, being higher in girls (21,9%) than in boys (10,1%), and obesity was 17,3%, being higher in boys (24,5%) than in girls (9,7%). A higher percentage of fat (36.9%) measured by arm fat area (AFA%) was found in girls. Instead boys had more central adiposity by applying the waist-hip ratio (0,86 ± 0,05). Conclusions: The schoolchildren studied are in alarming situation regarding the condition of overweight and obesity. Even, the situation has worsened compared to data from previous studies, which highlights the importance of controlling these parameters from an early age.