1,2,4-Oxadiazole is a well known heterocyclic compound containing an oxygen atom and two nitrogen atoms in a five-membered ring and widely studied by researchers because of their many important chemical and biological properties. This book gives idea about the synthesis of novel 1,2,4-oxadiazole derivatives as well as pharmacological importance 1,2,4-Oxadiazole derivatives. In recent years the number of scientific studies with these compounds has increased considerably. Taking into account the importance of these compounds to both heterocyclic and medicinal chemistry, we have decided to present the main synthesis approaches used for obtaining the heterocyclic nucleus, as well as the broad spectrum of pharmacological activities reported in the literature over the past twelve years. Presented spectra of the synthesized compounds in this book will also give the idea about various spectroscopic methods like 1H NMR, 13C NMR, MASS Spectra and IR spectra.