The present study was conducted to evaluate the in vitro antimicrobial properties of essential oil and different extracts of Eucalyptus citriodora. Eucalyptus citriodora is the genus which belongs to family Myrtaceae, kingdom plantae. It is an important medicinal plant. It has been known to produce several natural substances having antagonistic activities against several pathogenic microorganisms. The essential oil and extracts of Eucalyptus citriodora posses? strong antimicrobial properties and therefore can be used as natural preservative ingredient in food and/or pharmaceutical industry. The antimicrobial nature of the fractions was apparently related to their high Phenolic content and phytocehmicals. This book is mainly helpful for plant pathologists, food technologist, and pharmaceuticals.