Since 1980s decentralization seems to be a widely accepted strategy in the area of development administration accompanied by the expansion of democratization proeess at lower levels of government. As a development strategy, its popularity has not been reduced so far, now decentralization has been given more recognition. "The literature on development in recent years has been re-emergence of the debate on decentralization both as an important condition for achieving sustainable and as a fundamental goal in good government 2000:26). Thus decentralization seems to be an immerging issue reflecting an attempt towards more democratic and participatory approach to development, aiming at good governance which is associated with the ideas of liberal democracy There has been a considerable discussion on decentralization concerning the experiences related to both developed and developing countries. However only a few scholars have attempted to explore its underlying assumptions and theories. The purpose of this paper is to review and examine the existing theories and concepts relating to decentralization. At the beginning of this paper it discusses meaning, assumptions, various forms and theories related to decentralization. The latter part of the paper involves desirable and undesirable aspects of decentralization. However whether those arguments are good or bad are in the mind of the observer. In order to have any success of decentralized program, prior understanding of the term seems to be paramount important. This is an attempt to provide introductory and useful guidelines to those who are interested with the subject