The aim of the present study was to investigate the association between Collagen 1 alpha 1 (COL1A1) polymorphism and osteoporosis in DEXA verified 349 (145 osteoporotic, 87 osteopenic and 117 normal) postmenopausal women of India, who were not taking hormone replacement therapy. Two single-nucleotide polymorphisms (SNPs), that is, -1997G/T (rs1107946) and +1245G/T (rs1800012, Sp1) of the COL1A1 gene, were analyzed. Minor allele frequencies of rs1107946 and rs1800012 were 0.15 and 0.20 in osteoporotic women, 0.18 and 0.18 in osteopenic and 0.20 and 0.17 in women having normal bone mass. An allele dose effect with BMD of lumbar spine has been exhibited by major allele G of rs1107946 (GG: 0.86 g/cm(2), GT: 0.91 g/cm(2) and TT: 0.93 g/cm(2)) and minor allele T of rs1800012 (GG: 0.91 g/cm(2), GT: 0.87 g/cm(2) and TT: 0.81 g/cm(2)). Disease association analysis revealed a haplotype GT that confers approximately threefold higher risk of osteoporosis in the carriers (OR 3.12, 95% CI 1.24-8.88, P = 0.008) after adjusting the confounding effect of age, BMI and years since menopause. These results suggest that GT haplotype of COL1A1 gene is associated with a higher risk of postmenopausal osteoporosis in Northwest Indian women.