Progress in medicinal chemistry and in drug design depends on our ability to understand the interactions of drugs with their biological targets so that the knowledge of the physicochemical properties of compound , pharmacokinetics , pharmacodynamics and the factors that affect the pharmacological activities such as stereochemistry are important. Furthermore, the quantitative study of the role of substituents and their positions in the drug molecules on the physicochemical properties of (QSAR) are essential. This book is valuable for medicinal, theoretical chemists, biochemists and pharmacologists , as well as for other scientists interested in drug design.