The aims of this study were: 1) to determine bone mineral density (BMD) in different age groups, 2) to determine the prevalence of low BMD, and 3) to determine the possible association between BMD and a number of risk factors in Norwegian premenopausal women. BMD of the lumbar spine (L₂–L₄), total body, and the hip (total femur, femur neck, and trochanter) were measured using dual-energy X-ray absorptiometry (Prodigy, Lunar) in 145 randomly selected women aged 13–39 years. Information on other factors thought to influence BMD was obtained through questionnaire and a clinical interview. The group aged 25–29 years had the highest mean BMD in the total body, lumbar spine, and total femur while the group aged 13–19 years had the highest mean BMD in the femur neck and the trochanter. The mean BMD values of Norwegian premenopausal women were 3.4–5.1% higher than US/European reference data (P<0.05). five="" percent="" of="" the="" study="" sample="" aged="" 20–39="" years="" were="" defined="" with="" low="" bmd="">Z-score <–2) using="" the="" standard="" values="" from="" this="" study.="" weight-bearing="" physical="" activity,="" body="" weight,="" body="" height,="" and="" age="" were="" positively="" associated="" with="" bmd,="" whilst="" menstrual="" dysfunction="" and="" previous="" pregnancy="" were="" associated="" with="" lower="" bmd="" in="" some="" of="" the="" measurement="" sites.="" the="" results="" show="" that="" the="" factors="" associated="" with="" bmd="" are="" extensive,="" and="" the="" strategies="" to="" prevent="" low="" bmd="" have="" to="" be="" multifactorial.="" a="" follow-up="" study="" should="" be="" conducted="" on="" the="" study="" sample="" to="" investigate="" actual="" mean="" bmd="" values="" and="" bmd="" changes="" through="">