Identification of risk factors for osteoporosis has been essential for understanding the development of osteoporosis. The collagen type I alphal (COL1A1) gene is suggested to be implicated in reduced bone mineral density (BMD) in osteoporosis. In the present study, the investigation of the effects of Spl polymorphic variants of COL1A1 gene on BMD values, and the determination of the association between COL1A1 Spl gene variants and osteoporosis risk factors in the context of gene-environment interaction in Turkish postmenopausal women were aimed. For the detection of COL1A1 Spl polymorphism, PCR-RFLP techniques have been used. BMD for lumbar spine (L1-L4) and hip (femoral neck and total hip) was measured by DXA. This study was carried out using a sample of 254 postmenopausal women. We observed a trend decrease in BMD values in the subjects with "ss" genotype having lower BMD of lumbar spine, femoral neck and total hip than those with "SS" and "Ss" genotype, however the differences did not reach statistical significance (P > 0.05). We also found that the frequencies of the BMD under mean values at the femoral neck (57.5%) and total hip (76.2%) increased considerably in the subjects carrying "Ss/ss" genotypes in combination of having family history of osteoporosis (61.5% for femoral neck) and smoking history (90.0% for total hip). This population-based study indicates that COL1A1 Spl polymorphism may contribute to the development of osteoporosis in combination of osteoporosis risk factors in Turkish postmenopausal women. (C) 2014 Elsevier B.V. All rights reserved.