OBJECTIVE: To investigate the association, if any, between serum concentrations of folate, vitamin B(12) and homocysteine in complete hydatiform mole (CHM).,STUDY DESIGN: Blood samples were taken from 37 women with CHM and 52 healthy controls in the first trimester of pregnancy. Serum was analyzed for folate, vitamin B(12) and homocysteine using electrochemiluminescence and chemiluminescence assay.,RESULTS: In patients with CHM, significantly higher mean levels of serum vitamin B(12) were encountered (247.21 versus 180.32 pg/mL, P = .012). Significantly lower mean levels of serum folate were found in patients with CHM as compared with controls (7.91 versus 10.72 ng/mL, P = .008). Homocysteine levels tended to be higher in patients with CHM, but the difference was not statistically significant (10.58 versus 8.79 nmol/mL, P = .104).,CONCLUSION: This is the first report to suggest an association between folate, vitamin B(12) and CHM. Folate may play a protective role in preventing CHM.