Recent studies in western countries have indicated that women with low serum folate before pregnancy have greater risk of giving birth to babies with neural tube defects, and preconceptional folate supplementation has been recommended to prevent such defects. To determine whether Thai women needed folate supplementation before pregnancy, we carried out a cross-sectional study from September 2001 to January 2002. The objectives were to determine serum folate levels among women of child-bearing age and their relationship to dietary folate intake. One hundred and sixty-five apparently healthy, volunteer women aged 15 - 45 years were recruited from the Family Planning Clinic, Mother and Child Hospital, Health Promotion Centre, Region I, Bangkok. Data on general characteristics, nutritional status and dietary folate intake were recorded while venous blood was drawn for serum folate analysis. Results showed that 65.5% of the study group had low dietary folate intake, that 18% had low serum folate, and that there was a significant correlation between dietary intake and serum level (r = 0.68, P<0.001). There were also significant correlations between serum level and body mass index, (r =0.13, P<0.001). However, there were no significant associations between serum level and age, educational level, occupation, family income, or duration vegetables were stored in the refrigerator before consumption. In conclusion, there is preliminary evidence that some pregnant Thai women may have sufficiently low serum folate levels to put their babies at risk. We recommend further study on a larger scale to confirm whether folate supplementation is needed for Thai women at child bearing age. In the interim, it may be wise for obstetricians to measure serum folate in pregnant women to determine whether folate supplementation is required.