Lactose or milk sugar is a disaccharide composed of glucose and galactose, and is the primary carbohydrate found in mammalian milk. Lactose must be hydrolyzed into the simple sugars (galactose and glucose) to be absorbed by the small intestine. Lactase is an enzyme produced in the mucosa of the intestine that catalyzes the breakdown of lactose. Lactose intolerant children show low levels of lactase activity, and as a result, undigested lactose moves into the distal bowel. Here, symptoms such as bloating, cramps, diarrhea, flatulence and the production of gases occur in children (and lactose intolerant individuals’ in general) as the undigested lactose is fermented by bacteria. One of the health consequences of lactose intolerance (LI) in children is a reduction in calcium intake due to their avoidance of mammalian milk. Because of the problems associated with LI, many lactose-free food products are manufactured by the food industry. This chapter discusses LI in children, key symptoms of LI, methods to diagnose lactase insufficiency, lactase supplements, lactose-free food products and their health benefits and risks, and finally, the world market for these products and regulations and guidelines for industrial manufacturers.