The subject of unicameralism is literally centuries old. From the 9th century to the 18th century, many of the countries of Europe had established modified forms of the singe-house legislatures. Since then, tendencies toward the change of the legislative system have been manifested in many countries. After making a brief study of the trend of unicameralism in other countries including the United States of America, the writer has made a short review of the legislative systems that the Filipino people have had from the establishment of the short-lived Philippine Republic up to the adoption of the Constitution of the Philippines. The study also includes the analysis of the structure and functions of the National Assembly and a unicameral system of legislature.