AbstractThe endosteal and periosteal diameters of the second metacarpal were measured at the midshaft on radiographs of 62 normal girls at 11.0 ± 0.5 years (pre‐menarche) and again at 16.0 × 0.5 (post‐menarche). There was an average increase in the periosteal diameter of 10% and an average decrease in the endosteal diameter of 16%, both changes significant at p<0.01. Individual variability was greater for the endosteal than the periosteal surface changes (p<