The Sp1 polymorphism in the first intron of the collagen Ialpha1 gene was recently described to be associated with low bone mineral density (BMD) and increased fracture risk in Caucasian populations. The impact of this gene was assessed in a Southern Chinese population. One hundred and eighty-one women, aged 51.1+/-8.8 yr were evaluated for the Sp1 polymorphism. Twenty-two per cent of the women were classified as having osteoporosis on the basis of a T-score at the lumbar spine or the hip below -2.5 with or without a prevalent fracture. Genotype analysis was performed by PCR amplification and restriction enzyme digestion. Single-strand conformational polymorphism analysis (SSCP) was performed in 65 randomly selected samples to search for any polymorphic site in the PCR amplified region. The results showed that no restriction enzyme site could be identified in any of the 181 samples analyzed. Moreover, SSCP analysis revealed no polymorphism in the PCR amplified region of the first intron of the collagen Ialpha1 gene. In conclusion, the "s" allele, associated with low BMD and increased fracture risk in Caucasians, is non-existent or very rare in the Southern Chinese population. The absence of this "high risk" allele may in part account for the reduced fracture risk observed in the Chinese in comparison to Western populations.