This book is devoted to the study of inventory systems with special focus on deteriorating items inventory. Inventory System is one of the main stream of the Operations Research which is essential in business enterprises and Industries. Interest in the subject is constantly increasing, and its development in recent years closely parallels the development of operations research in general. Some authors even claim that "More operations research has been directed towards inventory control than toward any other problem area in business and industry" and among these the deteriorating items inventory have gain large emphasis in last decade. This book contains basic terminology of inventory systems, brief history and different inventory model of deteriorating items inventory with some realistic assumptions. This book should be useful to post graduate and research student in industrial engineering, production engineering, operations research, management science, business administration and related field.