This book intends to contribute facts and ways for the development of Theravāda Buddhism by providing an analytical and critical study of the current condition of Theravāda Buddhism through a historical survey. It explores the previous and present status of Theravāda Buddhism through its two main functions, such as Pariyatti (learning) and Paṭipatti (Practice), together with a detailed investigation of the various perspectives of scholars and seeking ways for the sustainable development of Theravāda Buddhism in the 21st century.