A representative sample of 285 70-year-old Danish women were examined by case history, 125I photon absorptiometry of both forearms (BMC), and lateral X-rays of the spine. Fat mass was calculated from height (H), weight (W) and estimated lean body mass (LBM) as W-LBM/H kg m-1. Seventy-five participants with previous or present disease or treatment known to influence the calcium metabolism were excluded. The remaining 210 women included the final study groups of seventy-seven long-term smokers and 103 non-smokers. Within both groups BMC correlated positively to fat mass, r = 0.447 and 0.560, respectively (P less than 0.001). The slopes of the regression lines and their positions were similar (P greater than 0.05). Hence, for a certain degree of overweight smoking per se does not influence BMC to a significant degree. Although the smokers were less obese (P less than 0.005) and tended to have lower BMC (P less than 0.10) their frequency of non-violent post-menopausal fractures, 40.3%, was the same as for non-smokers, 44.7%. The respective frequencies of definite osteoporotic fractures (i.e., spinal crush and fractures of the hip, proximal humerus and distal forearm) were comparable as well. In conclusion, the influence of smoking on the female skeleton seems mainly to be caused by the associated slenderness.