Infectious diseases create challenging problems in agriculture as well as in human health case. Though many antibacterial drugs are available for the treatment of human diseases, increase of new and reemerging diseases dramatically reduce the action of them. Since time immemorial plants have been used as one of the major sources for preparing drugs in modern as well as traditional systems of medicines. Therefore,systematic screening of plants may result in the discovery of novel antibacterial compounds.In this study antibacterial effect of fruit of Vitex negundo(Tamil- Nochchi)and bulbs of Allium sativum(Tamil- Ulli)were tested against some selected plant and human pathogenic bacteria. The results indicates the presence of active ingredients in the crude extracts.The ethyl acetate and ethanol extracts of fruit of Vitex negundo and bulb of Allium sativum could be used for further isolation and purification of novel lead molecules.This book, therefore provides further information regarding the bio-activity of these two plants and the results should be useful to professionals in drug discovery,or anyone else who may be interested to do research in medicinal plants.