World is rich in medicinal and aromatic plants which are used as natural health care products in Traditional Systems of medicine. Medicinal Plants are growing bundle in the wild or are cultivated on farmlands. As such, this tremendous wealth of nature finds itself limited to a particular locality. The knowledge of medicinal properties, of a particular plant species by the natives, known as Ethnobotany, is therefore the only way to learn about the usefulness of a particular plant species. Only a well qualified taxonomist is capable to properly identify and collect desired medicinal plant species. Even, then chances of mixing a plant species with its closely related species cannot be ruled out. In this book we have therefore attempted to compile data based on taxonomic and chemical studies to determine the authenticity of particular folk medicinal plant. In this, we have selected medicinal plants of different families and have develped practical botanical and chemical methods for their complete authentication.