The objective of this study was to investigate the relation of serum calcium level, body mass index(BMI) with bone status expressed as broadband ultrasound attenuation(BUA) measured by quantitative ultrasound (QUS) and the occurrence of osteopenia among adult men and women. Two hundred eleven(63 male and 148 female) workers who worked in 4 different battery factories were recruited from March 2005 to October 2005. BUA was used as a surrogate of bone mineral density and measured at left calcaneous bone area. The BUA value transformed into T-score by WHO standard conversion criteria to determine osteopenia (-2.5<t-score<-1.0). Serum calcium(Ca) was analyzed from fasting venous serum. Information on age, gender, smoking and drinking status were collected using questionnaire. Results of one-way ANOVA did not show any differences in BUA and serum calcium levels among different BMI groups in both men and women. BUA was correlated with age(r=-0.335), weight(r=0.326), height(r=0.382) and serum Ca(r=0.192). BMI and serum Ca showed significant main effects on BUA after adjustment with age, sex, smoking and drinking. In the logistic regression analysis of serum Ca and BMI on the prevalence of osteopenia after adjustment of related covariates, only BMI showed significant protective effect on risk of osteopenia(OR=0.855, 95% confidence interval=0.768, 0.951). When weight and height were added to the logistic regression model separately rather than as BMI value, weight showed a significant protective effect(OR=0.937, 95% confidence interval=0.897, 0.980), while height did not show a significant effect on the risk of osteopenia. This study confirms the protective effect of BMI on bone mineral density. The protective effect of BMI may be mainly attributable to weight rather than height.