For many years, investigators have been concerned with mechanisms that control and alter genetically regulated development. An intriguing aspect of these mechanisms is the ability of environmental factors to induce certain metabolic processes. Animal studies have shown that dietary manipulation of cholesterol and fatty acid metabolism during development can have persistent and permanent effects. In addition, there appears to be a critical period when changes in the diet can have lasting consequences. The changes in the control exerted by nutritional factors on metabolic development coincide with three phases of development: prenatal, suckling, and weaning. The effects of diet on cholesterol and fatty acid metabolism throughout these three phases of development will be addressed in this review.