Choline is a ubiquitous water soluble nutrient, often associated with the B vitamins; however, not yet officially defined as a B vitamin. It is important in the synthesis of phospholipid components of cell membranes, and plasma lipoproteins, providing structural integrity as well as being important in cell signaling; it is also important in the synthesis of the neurotransmitter acetylcholine, and the oxidized form of choline, glycine betaine, serves as an important methyl donor in the methionine cycle. It is present in a wide variety of foods, and is endogenously synthesized in humans through the sequential methylation of phosphatidylethanolamine. The present article represents an introduction to the nutrition, metabolism, and physiological functions of choline and choline derivatives in humans. The association of choline and choline derivatives in risk of chronic disease, including: neural tube defects, coronary artery disease, cancer, Alzheimer's disease, dementia, and memory, and cystic fibrosis is reviewed.