The identification of intrauterine growth retarded infants remains a problem. It is useful to distinguish between small for date which uses the reference of a statistical birthweight limit and intrauterine growth retardation. A study comprising nearly 100,000 births from many French regions allowed a definition of the limits of birthweights taking into account gestational age, sex, birth rank, maternal height and pregravid maternal weight. This new approach distinguished two groups of newborns, the "constitutionaly small" and those who are newly called "growth retarded". The validity of this new classification is discussed.