The objectives of this thesis are to study the being and the development of Bhikkhu and Bhikkhuni in Tharavadha Buddhism, to study the structure of management of Bhikkhu and Bhikkhuni in Tharavadha Buddhism, and to study the relationship between Bhikkhu and Bhikkhuni in Tharavadha Buddhism.

This research is a qualitative one that emphasizes the documentary research based on the primary source, i.e. the Tipitaka and the Commentaries, including the other academic works and the concerned researches.

From the study, it is found that, in the time of the Buddha, there are three types to ordain the Bhikkhu : 1. Buddha ordained a monk by himself called Ahibhikkhu Upasampada,  2. the ordinator praised three refuges, namely, Buddha, Dhamma, and Sangha called Tisaranakhom Upasampada, and 3. the Buddha allowed Sanga to ordain monk by Sanga praised four Yaties called Yatijadhutakarma Upasampada which is used nowadays.  As for being Bhikkhuni, it was said that the status of woman and the Bhram society was the condition to ordain.  So the Buddha ruled 8 kharudhams to one who wanted to be Bhikkhuni.  And the developments of the ordinations were Yatijadhutakarmavaja from only Bhikkhu and then Atthavajika Upasampada that were ordained from both Sangas and hold the 8 kharudhams for lifetime.  Before ordination should be Samaneri and Sikkamana for two years, and because there was not enough place to live, Buddha allowed the ordainer ordained two years per one Bhikkhuni that made Bhikkhuni not expand like Bhikkhu.  Nowadays, in Tharavadha Buddhism said that there have not Bhikkhuni, there have only Bhikkhu, and so they can’t ordain Bhikkhuni any more.

                 The structures of Bhikkhu’s administration, in the time of the Buddha, hold Dhamma-Vinaya to manage.  The Buddha authorized Sanga.  The managements are divided to groups and sections, i.e. Uppacha, Ajarn, Satthiviharik, Untavasik and monk who were selected to response a special duty, such as in robe, food, shelter and medicine.  As to Bhikkhuni, managed like Bhikkhu, except special duty, Buddha allowed Bhikkhuni to help together, that was provisional responsibility.

            The relationship among Bhikkhu and Bhikkhuni by respect to Dhamma-Vinaya, Bhikkhuni must respect Bhikkhu even though he was just ordained in that day.  Bhikkhu must take care of Bhikkhuni like their sisters, and another relationship, such as, in management, the four requisites, education, administration, propagate and generous to upasaka and upasika.  The Bhikkhu and Bhikkhuni respected Buddha by using Dhamma to practice themselves to be beyond suffering and help the other to leave out suffering and become peaceful in social lives.