Peri-apical radiographs have been used to identify women with low bone mineral density (BMD) in various parts of the skeleton, but their usefulness for men has not been elucidated. The aim of this study was to test if the mandibular bone structure and bone mass in men and women were related to the BMD of the forearms, determined by dual X-ray absorptiometry, in 42 men and 42 women (aged 18-84 yr). Mandibular alveolar thickness was measured in casts, and alveolar 'bone mass' was estimated on digital radiographs using gray-shade distribution. Alveolar bone structure was evaluated visually (trabecular pattern) on analog radiographs and with its bone texture on digitized radiographs. Bone texture was correlated to BMD in both men and women. BMD was correlated to alveolar bone mass and trabecular pattern in women, but not in men. Bone texture and body mass index (BMI) explained 57% of the variance in BMD for men, whereas trabecular pattern and age explained 50% of the variance in BMD for women. Sparse trabeculation was associated with osteopenia. We conclude that alveolar bone texture and BMI are predictors of BMD for men, and age and trabecular pattern are predictors of BMD for women.