Close relatives in families who have a child with a neural tube defect (NTD) are at greatly increased risk of having an affected child. Periconceptional folic acid reduces the risk of both occurrence and recurrence of NTDs substantially. Public health authorities currently recommend that the diets of all women between the ages of 15 and 44 who are capable of becoming pregnant be supplemented with folic acid tablets daily. We wondered if relatives in NTD families were more likely to use folic acid. From data obtained by interview with uncles and aunts in Irish NTD families we evaluated folic acid use in 144 of their pregnancies occurring between 1990 and 2000. There was a significant trend towards increasing use of folic acid both before and during pregnancy over the 10 years covered by the study. During the most recent years, 1998-2000, 57.9% of pregnancies reported by aunts were supplemented beforehand and 89.5% during the pregnancy. Pregnancies to smokers were significantly less likely to be supplemented with folic acid. In this study close relatives of an NTD child were more likely to report periconceptional folic acid use than the general public. While these results are encouraging, more remains to be done to ensure in this high risk group to ensure that the full prevention potential of folic acid is realised.