This textbook discusses the inter-relationships between infections and nutritional status. It deals with the fundamentals of the immune function of the human body and the role that nutrition and nutrients play in its optimal functioning. The role that infective processes play in the etiology of malnutrition and the relationships between poor nutritional status and risk of infections are described. There are chapters describing nutrient deficiencies e.g. vitamin A, and the risk of infections, and chapters on specific infections e.g. TB, AIDS, and their role in poor nutritional status. Specific coverage is given to those people most at risk from infections - infants, children and the elderly.