In this article much of the available data on lung volumes and mechanics in normal infants is assessed and summarized, and growth charts for the various parameters of lung function during the first year of life are presented. There is considerable evidence to show that lung development proceeds in a highly organized manner, and that strong linear relationships exist between lung volume and body size, between dynamic compliance and lung volume, and between airway conductance (the reciprocal of airway resistance) and lung volume. However, the latter relationship is affected both by the race and postconceptional age of the infant. Specific Airway conductance is higher during infancy than at any other time during life, and this gives the newborn infant certain advantages with which to counterbalance both the small size of his lungs and the fact that he is an obligatory nose breather.