1. In groups of South African Bantu and Caucasian women aged 30–44 years, sub-divided into those having had (i) none to two or (ii) seven or more children, measurements of radiographs of the second metacarpal and of the humerus were made in respect of length, cortical thickness, cortical index, cortical area/total area, cross-sectional area index and cortical/surface area ratio.
2. In Bantu mothers of large compared with small families, there were no significant differences in the means of corresponding variables. This was also the case with the Caucasian mothers. Bantu mothers of large and small families had significantly lower mean values for most variables compared with those of Caucasian mothers of large and small families. In all four groups, ranges of measurements and indices were very wide.
3. It is questioned whether Bantu mothers accustomed to a low calcium intake and to numerous pregnancies and long lactations, suffer from calcium deficiency. The problem of whether the high recommended allowances of calcium during these periods confer a clinically detectable benefit requires re-examination.