Leishmania donovani is the causative agent of visceral leishmaniasis worldwide. One of the unique features of this unicellular kinetoplastid protozoan parasite is that they have a bisubunit type IB topoisomerase unlike other eukaryotic counterparts and thus it is a potential target for anti-leishmanial therapy. Chapter 1 of this book describes in detail the effect of ATP on the type IB topoisomerase of Leishmania and is aimed for a better understanding of topoisomerase biology in this unicellular protozoan parasite. Leishmaniasis is a dreaded disease of mankind. Chapter 2 of this book describes the effect of cryptolepine on Leishmania donovani and deals with identification of new drugs and new therapeutic strategies to combat Leishmaniasis. This chapter describes how these unicellular parasites use autophagy as a survival mechanism in response to cellular stress. This book is aimed for all those who are interested in Leishmania and I hope this will also be of good reading experience for all those who have interest in biochemistry and cell biology.