The world in the 21st century is marked by high population mobility. When an increasing number of people have chosen to leave their motherlands and resettle in a new country, of those issues that have concerned the government, academics and the public throughout the world, urban sprawl is one of the most prominent. There are conflicting views toward this growing trend. While it has been taken as a positive development in many newly emerging cities, it is increasingly perceived as a threat to urban environment and considered as a trigger for numerous urban problems. The objective of this article is to evaluate the forces behind this trend and its consequences regarding to UN-Habitat program, based on the experiences of successful cities in the world to reveal the theoretical and practical aspects of what is currently known as a sustainable urban development on a global scale. The principles derived from the evaluating, are proposed to be used in sustainable development of Tehran city in Iran.