The following research study is carried with the objective of examining the most critical health and livelihood issues facing residents of informal settlements. It is worth noting that informal settlements now house a substantial proportion of the urban population in Africa, Asia and Latin America. A premise is then set to help identify interventions to improve health in the foregoing areas. The review begins by discussing urbanization as a major public health challenge for the 21st century, as urban populations are rapidly increasing, basic infrastructure is insufficient and social and economic inequities result in the formation of informal settlements. People over there suffer disproportionately from ill-health throughout their lifecourse and are more likely to experience disease, injury and premature death and ill-health may combine with poverty to entrench disadvantages over time. The health of both individuals and communities is affected by built and social environments surrounding them as evidence in this study suggests, and these settlements are plagued by profound environmental hazards and ingrained deprivations that cannot be suitable for a healthy life. The study further tackles in depth the factors which exacerbate ill-health in informal settlements and encourages prevention and early intervention as measures more effective than exhorting individuals to change their behaviour. This is due to the fact that changing behaviour becomes more farfetched in the light of their surrounding work and study environments. The concluding section examines a range of urban interventions to be taken into consideration when trying to upgrade and achieve health equity in these areas.