Although the pathophysiology of rickets and especially the central role of Vitamin D in this disease has been clarified since the 1920s, it is not completely understood why rickets is still prevalant in sunny countries. Furthermore, as we understand more about rickets, it appears that rickets is a heterogeneous disorder caused by vitamin D and/or Ca deficiency. Serum 25 and 1,25 OH vitamin D levels show a wide range of variation among children with rickets and the response to treatment is also variable. These observations suggest that individual susceptibility may play a role in the development of rickets. Polymorphisms in the Vitamin D receptor (VDR) gene were postulated to be associated with bone mineral density. VDR gene polymorphism could be influential in the development of rickets in some children as well. However, data in this regard are still scarce.