Vitamin A is an essential fat-soluble vitamin with a myriad of functions including cell differentiation, redox homeostasis, growth and immune functions. Systemic inflammation has been linked with oxidative stress and has been also associated with reduced serum concentrations of Vitamin A. This book examines the protective effect of Vitamin A on lung function and cancer, chronic obstructive pulmonary disease, and coronary heart disease. Also discussed is Vitamin A and its natural derivatives, the retinoids, which participate in several biological events necessary to the maintenance of tissue homeostasis, cell cycle regulation and cell differentiation and apoptosis.