Folic acid fortification of enriched cereal-grain products (which became mandatory in the U.S. on January 1, 1998) was intended to increase folate intake among childbearing-aged women to reduce their risk of neural tube birth defect (NTD)-affected pregnancies. Interest now focuses on assessing the effects of fortification on risk of NTDs and on folate intake relative to homocysteine (Hcy) concentrations and risk of vascular disease, although a causal relationship between the latter two has not been demonstrated. Increased serum folate levels were first reported in 1999. Data from the Framingham Offspring Study cohort showed increased mean serum folate in middle-aged and older adults; additionally, the prevalence of high Hcy concentrations had decreased by approximately 50% in subjects examined before (1995-1996) and after (1997-1998) fortification. Another analyses of samples collected between 1994 and 1999 identified a trend of increasing serum folate values from 1996 onward with values in 1998 160% of those measured in 1996. Comparisons between 1988-1994 National Health and Nutrition Examination Survey (NHANES) III data and 1999 NHANES showed increased serum and erythrocyte folate concentrations among childbearing-aged women. While recent data show improved folate status in a short period of time, much about long-term effects of the fortification program remains unknown. Interest in the effects of increased folate intakes on risk of NTDs or vascular disease needs to be balanced against concerns about masking the anemia of vitamin B-12 deficiency and the general lack of data about safety of continuous high intakes. Careful monitoring over time is necessary to determine that the program functions as intended.