The definition of 'natural' is 'produced or existing in nature.' Natural products refer to as any natural constituents, natural substances, or a group of the secondary metabolites that derive from plants, insects, marine plants and animals through their own metabolic pathways. Natural products are usually of high value and small quantity, and they have a variety of biological activities. Extensive research has been performed to understand the effects of natural products on the immune and inflammatory systems. However, the results have been published individually focusing on a particular aspect of immunity or inflammation. The readers in this field may benefit from a comprehensive review book that describes different aspects of immune/inflammatory responses together. This book provides an overview of how a variety of naturally occurring compounds may influence the body's immune and inflammatory systems with an emphasis on the actions of medicinal herbs. In this book, experts in each field present their recent data on the mechanisms by which natural products influence the immune and inflammatory responses. The experimental results that are described in this book are based on various in vitro as well as in vivo model systems. It is also discussed how such effects of natural products are related with their therapeutic applications for the treatment of immune and inflammatory diseases.