The present book, in its original Thai version, is a part of a large volume entitled “Buddhadhamma”, occupying 21 out of 1,145 pages (approx. a 55th) of the whole work.  The “Buddhadhamma” is divided into two main parts, namely, Part I on the Middle Teaching expounding the knowledge of nature and the natural law, and Part II on the Middle Way dealing with the Buddhist practice which consists in the application of that knowledge to the creation of the Noble Life. The Middle Way or the practices as described in Part II is defined as the Noble Eightfold Path. Of the eight factors of the Noble Path, Sammsati or Right Mindfulness is the seventh one. It is this seventh factor of the Noble Eightfold Path that is the subject matter of the present translation, as evidenced in its title, Sammsati : An Exposition of Right Mindfulness.         The Thai version of Sammsati was published separately as a booklet by the Dhamma Study-and-Practice Group towards the end of B.E. 2528 (1985 C.E.). “Dhamma-Vijaya”, the present translator, read the original Thai version. He found it interesting and helpful to the practitioner of Buddhism, and took upon himself the task of translating it into English. It is, consequently, through the effort of Dhamma-Vijaya that this English version of the Sammsati has come into being. Not only encouraging the translation of the work into English, Khun Panita Angchandrpen has but also been enthusiastically urging the publication of the translation and has intently overseen the book through the printing process. It is through her zealous and active goodwill that this English version has come to appear in the present book form. In place of a compositor, Phra Mah Insorn Cintpao Duangkid has relentlessly managed to get through the whole task of word processing. His increasing mastery of Desktop Publishing on a microprocessor has rendered the production of the book labour-saving, time-saving and money-saving. My thanks go to all whose names are above mentioned for their generous help in bringing about this publication and to Khun Panya Vijinthanasarn for the design of the cover.                                                         Phra Debvedi (Prayudh Payutto)                                             May 15, B.E. 2531 (1988 C.E.)