Folate is an essential micronutrient, and its nutritional inadequacy is widespread; hence, programs to increase its intake are necessary. However, many concerns about possible adverse effects due to excesses have been raised. Serum folate levels are directly correlated with intake and, when low, are associated with neural tube defects (NTD), high blood homocysteine levels, and megaloblastic anemia. Serum folate cutoff points have been identified for each abnormality, and all can be associated with intakes related to the current recommended dietary parameters. Likewise, high intakes that overwhelm the physiological capacity to process folic acid into biologically active folate derivatives are near the recommended tolerable upper intake level. Although we do not know with certainty the minimum efficacious dose that prevents all folate-dependent NTD, it may actually be much lower than the current recommendation, especially when provided through food fortification; supplemental intakes around 100 microg/day appear to be appropriate.