Lung development is a methodical and co-ordinated process that culminates in the creation of an organ that contains airways, alveoli, blood vessels, multiple innate and acquired host defence systems, and processes to weaken the harmful effects of oxygen in the environment. By regulating cellular differentiation and branching morphogenesis, vitamin A plays an essential role during lung development. Retinoic acid is required for normal alveolar development and vitamin A administration increases lungs elastic fibre contents at birth. Additionally, several experiments showed that retinoic acid restores alveolar architecture to dexamethasone-treated lungs and maintains alveolar development in lungs treated with an angiogenic inhibitor. This book discusses and presents data on vitamin A and its role in lung development.