OBJECTIVE: To study the correlation between vitamin D receptor genetic polymorphism FokⅠand vitamin D deficiency rickets in children between 1 to 3 years old, and to explore the significance of hereditary factors in the development of vitamin D deficiency rickets. METHODS: Sixty-two children with vitamin D deficiency rickets and 60 healthy children as a control group were enrolled. Serum levels of 25-hydroxyvitamin D3 were measured using ELISA. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) genetic analysis method was used. A restriction fragment length polymorphism in the vitamin D receptor genetic polymorphism Fok I was tested. The frequencies of the vitamin D receptor genotype and allele were compared between the two groups. RESULTS: Serum 25-hydroxyvitamin D3 levels in the rickets group were significantly lower than those in the control group ( 9.1±4.1 ng/mL vs 16.1±6.9 ng/mL; P<0.05 ). FF genotype in the vitamin D receptor genetic polymorphism Fok I was more common in the rickets group than in the control group (53% vs 25%; P<0.05). F allele frequency in the rickets group was significantly higher than that in the control group (73% vs 57%; P<0.05). CONCLUSIONS: There is a correlation between vitamin D receptor genetic polymorphism Fok I and vitamin D deficiency rickets. This suggests that vitamin D receptor genetic polymorphism might play an important role in determining susceptibility to development of vitamin D deficiency rickets.［Chin J Contemp Pediatr, 2010, 12 (7):544-546］