The Epidemiolgy Branch (EBRP) is conducting a case-control study in Illinois and California to determine whether the use periconceptional vitamin supplements can reduce the risk of neural tube defects. Women having either a fetus or an infant with a neural tube defect are being ascertained through perinatal networks, vital records, and other sources and are being matched to two controls on maternal race and geographic locale. One control is a mother with a normal pregnancy, and the other the mother of an infant with a fetus with a major health problem. Cases and controls are being interviewed within 3 months of the end of pregnancy to determine whether those having a conceptus with a neural tube defect are less likely to have used vitamins in the periconceptional period. The study has been in the field for over a year. In California over 300 sets of NTD cases, normal controls and malformed controls have been identified and interviewed. In Illinois the corresponding figure is 100. This will provide an excellent number of subjects for analysis. Nonetheless, we intend to identify as many cases as possible born before May 1, 1987. This will require identifying new cases through July 1987 and new control subjects through October 1987. We hope to complete the data editing phase of the study and begin analysis by the end of 1987.