The relationship of folic acid to neural tube defects has provided us with one of the richest case studies in nutrition science policy of this half century. The concepts of nutritional adequacy in the periconceptual period, the power of well-designed and controlled intervention trials, the challenges of altering the intake of a critical nutrient, the risks and benefits of food for fortification, proper targeting with supplementation, and the effectiveness of achieving dietary change are all elements of this case study that we will continue to explore throughout the pages of this journal in the months ahead.