The aim of this study was to determine whether forearm bone mineral density (BMD) measurements are affected by clinical risk factors for osteoporosis to the same extent as spine and hip BMD. The study population consisted of 1,009 female patients and volunteers, of whom 238 were premenopausal. Women were placed into seven groups according to which clinical risk factor they had (women could be placed in more than one group): (1) atraumatic fracture since the age of 25 years, (2) report of X-ray osteopenia, (3) predisposing medical condition or use of therapy known to affect bone metabolism, (4) premature menopause before the age of 45 years or a history of amenorrhea of longer than 6 months' duration, (5) family history of osteoporosis, (6) body mass index (BMI) <20 kg/m(2), and (7) current smoking habit. Forearm BMD was measured using an Osteometer DTX-200 peripheral dual-energy X-ray absorptiometry scanner, and spine and hip BMD measurements were obtained on a Hologic QDR-4500 scanner. Manufacturers' reference ranges were used to calculate Z scores for the spine and forearm, and the NHANES III reference range was used to calculate Z scores for the hip. Multivariate regression analysis was used to estimate the mean decrease in Z score associated with each clinical risk factor. The Z-score reductions associated with the seven risk factors were similar for forearm and central BMD measurements. For forearm measurements, Z-score decreases associated with a history of atraumatic fracture (-0.25), a medical condition or therapy known to affect bone metabolism (-0.26), premature menopause or history of amenorrhea (-0.30), and BMI <20 kg/m(2) (-0.82) were all statistically significantly different from zero (P < 0.05). With an increasing number of risk factors in each individual, the mean Z score at each measurement site became progressively more negative. In conclusion, clinical risk factors for low BMD affect forearm BMD measurements to a similar extent as central BMD.