An association between bone disease and bone lead has been reported. Studies have suggested that lead stored in bone may adversely affect bone mineral metabolism and blood lead (PbB) levels. However, the relationship between PbB levels and bone loss attributed to periodontal disease has never been reported. In this study we examined the relationship between clinical parameters that characterize bone loss due to periodontal disease and PbB levels in the U.S. population. We used data from the Third National Health and Nutritional Examination Survey (NHANES III), 1988-1994, for the analyses. A total of 10,033 participants 20-69 years of age who completed a periodontal examination and had whole blood tested for lead were examined. Four types of periodontal disease measures were used to indicate oral bone loss: periodontal pocket depth, attachment loss extent, attachment loss severity, and the presence of dental furcations. We found that dental furcations were the best periodontal bone loss indicator for PbB levels (p = 0.005) in a multivariate linear regression model adjusting for sex, age, race/ethnicity, educational attainment, poverty status, smoking, and age of home. Furthermore, after additional modeling, we found a smoking and dental furcation interaction (p = 0.034). Subsequent stratified analyses indicated that current and past smoking is an effect modifier for dental furcations on PbB levels. These findings indicate that increased PbB levels may be associated with advanced periodontal bone loss, particularly among people with a history of smoking.