To study the bone mineral density (DMO) and the bone mineral concentration (CMO) in lumbar spine (L2 and L4) by dual-energy x-ray absorptiometry with a lunar DPX (DEXA) in a children sample of the community of Madrid; to relate the values obtained with the age, sex and pubertal development; and to compare the values of DMO found with the publications of other autonomous communities.351 children, 184 boys and 167 girls selected at random in our environment. The age range oscillated between 6 months and 20 years. Grouped in intervals of a year according to the sex; and in accordance with the pubertal development. The bone mineral content was measured by dual-energy x-ray absorptiometry with a lunar DPX in the lumbar spine at level of L2-L4. The statistic analysis has been accomplished with the SPSS version 6.0.1. They have been obtained the average and deviation standard for each group from studied age, and also according to pubertal development; the DMO and CMO of the boys and girls have been compared by groups of age; the DMO and CMO within each sex between a group of age and the immediately superior have been compared through an analysis of the variance; the effect that the age has on the DMO and the CMO has been evaluated and finally through multivariant analysis techniques the regression models have been estimated between the age and the DMO, and the age with the CMO.The DMO shows variations between the various communities and even in different samples of a same community, in Carrascosa study the DMO is highest, expressed in SD score, in many several groups of age studied with respect to our values and with the values of Moreno et al and Armadá et al; the values of DMO in our study are greater than the ones found by Moreno et al and Armadá et al; the first four years and the adolescence are the periods of maximum increase of the DMO, but it also increases in an oscillatory way in the intermediate stages; the girls present some highest levels of DMO in the groups of age of 12-13 and 14-15 years, probably in relationship to a most precocious beginning of the puberty; and finally the regression line of the DMO as compared to the age for both sexes are parallel and have equal court point, what means that they are coincident.