OBJECTIVES The object of this study was to determine the relative usefulness of clinical and radiographic indices in the diagnosis of patients with low skeletal bone mass amongst 135 healthy perimenopausal women, aged 45-55 years, attending for routine dental treatment. METHODS Bone mineral density was measured for the spine and femoral neck, using dual energy X-ray absorptiometry. Each patient's osteoporosis status was calculated according to the WHO criteria for Caucasian women. Each patient received a dental panoramic tomogram, and the width of the inferior mandibular cortex (mental index, (MI)) was measured. The body mass index (BMI) and simple calculated osteoporosis risk estimation (SCORE) indices were calculated. RESULTS The SCORE index was a significant factor in predicting low bone mass, but with the weight of the patient being the only significant constituent factor. MI, BMI and SCORE indices were significantly correlated with skeletal bone density. When the logistic regression model included MI, BMI and SCORE indices, all three variables were significant predictors of low skeletal bone mass. CONCLUSIONS A thinning of the mandibular cortices (MI<3mm) in a normal perimenopausal female is associated with low skeletal bone mass. If, in addition, the patient is underweight (BMI is below 20kg/m(2)) or has a high SCORE index (> or =6) then this increases their risk of osteoporosis.