Polymerase chain reaction was used to amplify across variable restriction sites of the COLI A1 and COLI A2 genes that encode the alpha 1 and 2 subunits of type I collagen. The relationship between these polymorphisms and bone mineral density (BMD) was studied in 683 Chinese men and women. In 100 men and women, COLI A1 Sp1 polymorphism was not found, which was consistent with other previous studies in Asian populations. However a statistically significant relationship was observed between COLI A2 Eco R1 and Puv II genotypes among the Chinese men studied. The mean BMD was consistently lower in men of the EE and PP genotype (P < 0.05 by analysis of variance [ANOVA]) than in men of the ee and pp genotypes. However, no association between BMD and the Eco R1 or Puv II genotypes was observed in Chinese women (P > 0.05 by ANOVA). We conclude that the COLI Al Sp1 binding site is absent in Hong Kong Chinese, whereas the COLI A2 Eco R1 and Puv II genetic polymorphisms may be associated with the BMD of elderly Chinese men.