The author present a new method of assessment of bone age derived from the analysis of carpal osseous development of 5,225 Spanish children and adolescents. The method is based upon the determination of a carpal index from the measurement of the largest diameter of the eight carpal bones, the proximal epiphysis of the first metacarpal and the distal cubital and radial epiphyses. There is a highly significant correlation of this carpal index with chronological age (P < 0.0001). From this index the author has set up an equation defining an index of evaluation of carpal ossification which helps to estimate bone age according to six different ranges of significance: significant retardation, moderate non significant retardation, borderline normality, complete normality, moderate non significant advance, significant advance. The method is simple to realize. It reduces the risk of errors in the evaluation of bone age due to asynchronisms of maturation of the ossification centres and to the individual subjective factor occurring with a morphologic assessment. Furthermore it takes into account the physiological variations of bone age on both sides of the mean normal value.