Toxicology is an interdisciplinary subject that requires the knowledge of many areas such as analytical chemistry both organic and inorganic, biochemistry, pathology and physiology. The book is designed to provide a wide ranging overview of the various toxicants and their effects on living organisms particularly of human begins. The book also provides the fundamental knowledge of the principles related to toxicology, chemical toxicology, environmental toxicology and related sciences, so as to meet the challenging requirements of students as well as teachers in environmental sciences, pharmacological, medical, veterinary, biomedical science and toxicological sciences. All essential aspects of toxicology have been covered in this book. It comprises 18 chapters in a logical sequence. Toxicology is distinguished by up-to-date insight into the harmful interactions between chemicals (xenobiotics) and biological synthesis. It gives better understanding on acute toxicology risk assessment, toxicity testing and many other areas directly or indirectly related to toxicology.