The range of fat corrected distal forearm mineral content (FMC) (at a site which comprises approximately 75% cortical and 25% trabecular bone) and the effect of aging on FMC were determined in normal premenopausal women. In 106 women (mean age 39; range 18-56) the mean FMC was 1.184 (SD 148) g/cm; fat correction increased this to 1.239 (SD 148) g/cm. There were significant correlations between fat corrected FMC and height, weight and BMI (r greater than 0.16; P less than 0.05). In 43 of these women (mean age 35; range 18-51) repeat measurements of FMC were performed. The last measurement was separated from the first by a mean time interval of 27 +/- 3 months. There was no significant change in uncorrected FMC (baseline 1.185 +/- 0.21 g/cm compared with their final measurement 1.182 +/- .020 g/cm; P = 0.51). Fat-corrected FMC (baseline 1.229 +/- .021 g/cm compared with 1.223 +/- .020 g/cm later) tended to decrease although this change was not significant (P = 0.06). Age ranked cusum analysis demonstrated a non-significant fat-corrected rate of change in FMC of -.3% yr in those over 35 years of age (P less than 0.10). This data suggests that if there is any distal forearm bone loss before the menopause it is negligible.