Neural tube defects (NTDs) are the second most common type of birth defect. In period of 201 1 til 20 1 5 in Croatia the incidence of NTDs were 4.75 on 10 000 births. Importantly, due to better prenatal diagnosis the incidence of NTDs is decreasing. The aetiology of NTDs is not known and NTDs are considered multifactorial disorders. Evidence so far suggests that in development of NTDs genetics and environmental factors are involved and some studies indicate importance of folate and/or folic acid deficiency. Folates are naturally occurring while folic acid is synthetic derivate of vitamin B9. Due to its stability and better absorption folic acid is used for supplementation and food fortification. Within the organism folates and folic acid are involved in numerous metabolic pathways such as synthesis of amino acids, nucleotides and DNA methylation, indicating that folates and folic acid are required in the processes that involve higher DNA synthesis as in embryonic cells. Studies conducted since 1970s indicate that supplementation with folic acid (alone or in combination with other vitamins) can reduce NTDs occurrence. Based on these results, in 1998 USA and some other countries introduced food ( cereals) fortification with folic a cid that has led to the decrease of NTDs occurrence in these countries for 10 to 80 %. Such fortification is not embraced in Croatia and other European Union countries due to involvement of folic acid in DNA methylation and possible development of cancers. Molecular mechanisms underlying development of NTDs are not known yet. Currently, several molecular mechanisms of NTDs development are investigated su ch as folate receptor on plasma membrane, nucleotide synthesis and DNA methylation. Knowledge on the molecular mechanism of NTDs development will point to the development of more effective intervention for treatment of NTDs.