Objective To investigate the effect of calcium supplementation on bone mineral density (BMD) in Chinese women with different FokI vitamin D receptor (VDR) genotypes (FF, Ff, and ff) after weaning or resumption of menstruation during lactation.Methods A total of 40 subjects with the same FokI VDR genotype were randomly divided into two groups: one received calcium tablet (600 mg once daily as CaCO3) and the other placebo tablet once daily for 1 year. At baseline, BMD was measured by dual-energy X-ray absorptiometry at lumbar spine (L2-L4) and at left hip whereas serum PICP, serum OC, and urinary CTX, serum 25(OH)VitD3, and serum estradiol were measured at weaning and 1 year thereafter.Results After the intervention, BMD at lumbar spine and at left hip increased significantly in all these women with a trend among different FokI VDR genotypes such as FF > Ff > ff (P