The use of synergist with insecticide may provide the most feasible way to prevent the development of resistant races of pests. The present book is divided into two parts. The first part sheds the light on resistance in insect pests, focusing mainly on the mechanisms of resistance, particularly metabolic resistance. The second part deals with some important aspects related to synergists and synergism, particularly the possible role(s) of synergists in insecticide resistance management and research. The book ends with a conclusion, which represents the author’s point of view about synergists and synergism. This book is of importance to the students of the Faculties of Agriculture and Science.