Although systematic vitamin D supplementation in adolescents remains debated, rickets is nevertheless a well recognized pathology in this age group. Adolescence is an at-risk period because of rapid growth, insufficient calcium intake and/or vitamin D status. Surveys have shown that calcium intake is insufficient (< 1000 mg a day) in 45% of boys and 71% of girls and that vitamin D status is deficient (25-OH-D < 10 ng/ml). The aims of the study carried out by the Calcium Group of the Société Française de Pédiatrie, were to evaluate the frequency of rickets, and to define the criteria for the adolescent population at risk. Forty-one adolescents with rickets were hospitalized between 1985 and 2000. Most of the cases were from the Northern France: 20 from Paris and suburbs, eight from the North-West, four from the North, four from the North-East; five were from the Center of France. The mean age was 13 years and two months for the 28 girls, and 14 years and four months for the 13 boys. Eighty per cent of the adolescents were from immigrant families (33/41): 15 were from sub-Saharan Africa, ten from North Africa, six from Pakistan and two from Turkey. Two thirds of the adolescents were hospitalized in the 2nd quarter of the year. Some adolescents suffered from lower limb pain, 16 had deformations of lower limbs, particularly genu valgum, associated with pain; seven others had either muscle spasms (4), tetany (3). Serum calcium level was low (average 1.84 mmol/l: [1.1-2.5]), and serum 25-OH D level was extremely low. Radiographic characteristics observed were metaphyseal strips on the knees, with condensed edges at times, with the presence of bone demineralization. The treatment combined calcium and vitamin D, and was often administered intravenously when a hypocalcemia was detected. Rickets is not frequent in adolescents, but nonetheless this pathology is not exceptional, and the number of cases is probably under-estimated. Rickets affects immigrant adolescents in particular but nevertheless could also present a certain risk period for the general population.