The aim of the research was to monitor the natural history of mild idiopathic scoliosis in school children, primarily those with a scoliotic curve lesser than 20 degrees according to Cobb who had been treated by regular observation and sports activities. A total of 97 children, 73 girls and 24 boys, aged between 9 and 14 years were enrolled. All the children were monitored for three years and in this period they were subjected to regular examinations and to at least three X-ray examinations. There were 51 thoracal, 39 thoracolumbar and 7 lumbar cases of scoliosis. After the three year observation period thoracic scoliosis improved in 56.9% of patients, 17.7% showed no change while 25.5% of the cases deteriorated. Nonprogressive thoracolumbar scoliosis was found in 76.9% of the cases, 12.9% showed no change from baseline while in 10.3% curve progression was noticed. Nonprogressive lumbar scoliosis was observed in 4 cases, in 2 cases the condition was unaltered while in 1 case curve progression was noticed. In the whole group there were 18.6% cases of progressive scoliosis. The results of this research have confirmed that regular observation and sports activities are the best methods of treating idiopathic scoliosis with a curve lesser than 20 degrees according to Cobb.