The purpose of this full length paper is to examine the essential links between the mega-city phenomenon and urban sustainability, with a view to inform in policy and strategies for the sustainable development of the mega-city of Lagos in Nigeria. The research method used is a case-study approach involving qualitative analysis of archival materials, publications of the Lagos State Government and its agencies; secondary data related to Lagos mega-city (including available census data); and other primary data from participant-observation - The author spent two years within the Lagos metropolis to observe and record the state and quality of physical and social infrastructure. The paper also reviews literature related to urban sustainability, the challenges of mega-cities in general and the context of Lagos as a particular case-study. Specific infrastructural priorities and sustainability dimensions are presented as lasting and tenable responses to the challenges. The author of this publication is Dr. Adetokunbo Oluwole Ilesanmi who lectures at the Department of Architecture, Obafemi Awolowo University, Ile-Ife, Nigeria. He obtained a BSc degree in Architecture in 1983, and was awarded the Faculty Prize for the Best Overall Student in the Faculty of Environmental Design and Management. Afterwards he got a MSc Degree in 1985 and was employed in private architectural practice until 1999 when he resumed academic career. Lastly he obtained a PhD in Architecture in 2006 from the Obafemi Awolowo University. His post-doctoral research interests include housing, urban design and urban studies; sustainable architecture; housing and health; building evaluation; design research; and built-environment education. A mega-city by definition is a continuous urbanized area with a population of at least 10 million people. The largest cities are no longer in the developed world but in the developing world, and these ones appear to have been growing at the most rapid rates. I develop three themes which I consider are relevant to this topic: 1. Challenges of emerging mega cities in the developing world. African mega-cities like Lagos face major urban challenges, such us high rates of immigration from the rural areas which don´t help with problems like unemployment, inadequate housing, food and water supply, pollution, and traffic issues. These cities are characterised by a conflicting mixture of excessive poverty and wealth, severe lack of jobs and great economic opportunities. In the case of Nigeria and Lagos and according to this publication, the issues coming from this rapid urbanization include: slums, overcrowding, poor sanitation, air and water pollution, clogged sewers, solid-waste contamination, and staggering urban traffic, illegal conversion of land-use and unbridled physical development without appropriate legislation, regulation and enforcement. 2. Infrastructure priorities. Some physical and social infrastructures that represent key areas of action in Lagos are housing, road construction and upgrading, integrated transportation systems, urban design, waste disposal and drainage Systems, Health care delivery, potable water supply and environmental sanitation, security of lives and property, and energy and regular power generation and supply. 3. Urban essentials. Some fundamental concerns of sustainability that could be described as ´dimensions of the sustainable city´ would be the following applicable in most of African cities: (i) Sustainable urban economy, which means work and wealth; (ii) Sustainable urban society, which means social coherence and solidarity; (iii) Sustainable urban shelter, which means decent affordable housing for all; (iv) Sustainable urban environment, which means stable ecosystems; (v) Sustainable urban access, which means resource-conserving mobility; (vi) Sustainable urban life, which means Building liveable city; and (vii) Sustainable urban democracy, which means empowering the citizens through participatory approaches. After reading this publication about Lagos, It seems an ideal example of mega-city to understand the workings of a massive African city; how it can continue to function as a city considering an acute lack of basic amenities and public infrastructure viewed as essential in traditional urban studies. As many other contemporary Africa´s largest metropolis, we mentioned that Lagos has its characteristics and faces an escalating crisis in terms of the provision of basic services such as water, housing and mass transit systems. One could think that the initial aspect to sort out in order to start thinking of all these issues is strengthening the Government´s organisations as nowadays they are characterized by inadequate technical and administrative expertise. As a positive critique of this paper, I think it is very constructive the way how the author offers policy recommendations from an architectural and urban design perspective relating to housing, urban renewal and transportation. I also agree with him when he concludes saying it is essential the need for all stakeholders to respect sustainable development principles, and engage in greater synergy on the future of mega-cities. The Doctor believes that, in the long-term, not only technological development but also better-informed urban policy-making and management can help to mitigate several of the problems of African mega-cities.