This article briefly summarises some of the problems of population increase.Population increase is comparatively modern, and due to a declining mortality rate rather than rising birth rates. Primary factors contributing to this decline are: an increase in the quantity of food, an increased amount of goods available for well-being, social reforms such as maximum working hours and minimum working wages, improvements in sanitation and hygiene, as well as treatments for disease and improvements in surgery. The existing population of countries, and the internal distribution of population, are subject to migration which can greatly increase problems. Internal migration is almost always from the countryside to the cities. Of the most serious aspects of the growth of the cities is waste disposal and air pollution, and the removal from cultivation of fertile land. If the problem of over-population is sufficiently general to be world-wide, it will be most serious where accompanied by low incomes and marginal living standards. Prospects of improvement for undeveloped countries in the immediate future lay mostly with increasing the food and water supply and increased aid. Since the main cause of the population crisis is decrease in mortality, ensuring an increase in mortality as a solution would probably be rejected by most. Other measures include restriction of births, improved food production, or otherwise the population increase can be allowed to continue.