Eucalyptus is a tree native to Australia, belonging to the myrtaceae family, and widely introduced throughout the world. This book provides the reader with the main information on the quantitative and qualitative, chemical and biological evaluation of certain secondary metabolites extracted from Eucalyptus leaves, with a view to exploring new active substances with a therapeutic effect. The species covered by this study are little studied. They are found in Tunisia, but also in other parts of the world such as North Africa, Madagascar, Mayotte, South Africa, Ivory Coast, Argentina, California, Portugal and the Mediterranean.This book is a practical guide to the extraction, identification and evaluation of the biological activities and health benefits of Eucalyptus essential oils. The main results have been validated by Doctor Jalloul Bouajila (Senior Lecturer at the Faculty of Pharmacy of Toulouse, Paul Sabatier University, France) and Professor Manef Abderrabba (Professor of Chemistry, IPEST, Tunisia).