Aim: To simultaneously investigate the contribution of the alpha 1 chain of col-lagen type 1 (COL1A1) and alpha2-HS-glycoprotein (AHSG) genes to the varia-tion of bone geometric parameters in both Caucasians and Chinese. Methods: Six hundred and five Caucasian individuals from 157 nuclear families and 1228 Chi-nese subjects from 400 nuclear families were genotyped at the AHSG-Sacl, COL1A1-PCOL2 and Sp1 polymorphisms using polymerase chain reaction (PCR)-restric-tion fragment length polymorphism (RFLP). 5 FN bone geometric parameters were calculated based on bone mineral density and bone area of femoral neck (FN)measured by dual energy X-ray absorptiometry. Population stratification, total family association, within-family association, and linkage tests were performed by the quantitative transmission disequilibrium test program. Results: The t-test showed the significant differences of all bone geometric phenotypes (except ED)between Caucasians and Chinese in the offspring using both unadjusted and adjusted (by age, height, weight, and gender) data. In Caucasians, we found significant within-family association results between the COL1A1-Sp1 polymor-phism (rs1800012) and cross sectional area (CSA), cortical thickness (CT),endocortical diameter (ED), buckling ratio (BR) (P=0.018, 0.002, 0.023, and 0.001,respectively); the COL1A1-Sp1 polymorphism also detected significant linkage with BR (P=0.039). In the population of China, the within-family associations between the COL1A1-PCOL2 polymorphism (rs1107946) and CT, BR were signifi-cant (P=0.012 and 0.008, respectively). Furthermore, evidence of linkage were observed between the AHSG-SacI polymorphism (rs4918) and CT, BR (P--0.042 and 0.014, respectively) in Caucasians, but not in Chinese. Conclusion: Our results suggest that the COL1A1 gene may have significantly association with bone geometry in both Caucasians and Chinese, and the AHSG gene may be linked to bone geometry in Caucasians, but not in Chinese. This study represents our first efforts on investigating the importance of the COL1A1 and AHSG genes n bone geometry in both Caucasians and Chinese.