Thiadiazole derivatives possess interesting biological activity probably conferred to them by the strong aromaticity of this ring system, which leads to great in vivo stability and generally, a lack of toxicity for higher vertebrates, including humans.Isatin ring system consists of pyrrole ring fused with benzene ring. Isatin and its analogs are versatile substrates, which can be used for the synthesis of numerous heterocyclic compounds. In the past few decades, Isatin and its derivatives have received much attention due to their chemotherapeutic values. These scaffolds have been consistently rewarded as a promising versatile lead molecule with a pivotal position in modern medicinal chemistry.A major aim of this book was to provide recent Biological potential of Thiadiazole and Isatin derivatives.