Foods, which, in addition to their nutritional attributes, contain also elements that are considered to be health-promoting, have been termed "functional foods". In this regard, human milk has gained recognition as being the ultimate functional food for infants - by its biological compatibility, nutritional value and the undisputed added value of its health promoting qualities. Intensive research activity has recently evolved in a quest to identify and define the components of human milk that might confer disease-preventing and health-enhancing properties and to determine the instances and clinical conditions in which these factors become particularly important. The outcome of such research would also provide a rationale for advocating the supplementation of commercial infant formulas with such substances. In effect, the body of data accumulated from scientific and clinical studies on nucleotides, probiotics, prebiotics and long-chain polyunsaturated fatty acids in human milk and as additives to infant formula, has become regarded as convincing enough by the infant formula industry so as to launch into the market formulas supplemented with one or more of these factors - in an effort to emulate human milk and its beneficial effects. The following review is intended for the reader to obtain a general idea of the new supplements that have been introduced to infant formulas. We summarize the pertinent experimental and clinical observations concerning each of the supplements, pointing out their potential specific benefits, their possible disadvantages and the issues that still remain unresolved.