Plants a wealth of secondary metabolites have been used for thousands of years to treat different ailments. A number of these natural products have shown biological and pharmacological activities and serve as the starting point in the development of modern medicines. Screening of crude plant extracts open the door for the way for discovery of novel bioactive compounds and elucidation of their structures leads towards new synthetic preparations, which can be administered in reproducible, accurate doses for particular therapeutic purposes. There is less known information about Samanea saman Merr., and Prosopis cineraria Druce. However, authors in this book present comprehensive information about traditional uses, biological and phytochemical investigation of Samanea saman Merr., and Prosopis cineraria Druce.