Currently, more than 7 billion people are living on Earth. Back in 1950, 2.5 billion people populated the planet. According to model calculations of the UN, this number could increase up to 10 billion in 2060 and up to 11 billion at the end of the century. This tendency is influenced by two demographic components: development of births and development of deaths. A perquisite to not significantly exceed the level of 11 billion people is a fertility decrease from 2.1 births per woman, which is the existing level, to 2.0. Currently, the world average fertility level amounts to 2.5 births per woman. However, there is a tremendous difference between industrial countries with an average of 1.7 and the least developed countries with 4.3. To reach the goal of 2.0 births or lower the least and part of the other developing countries need to significantly decrease their current fertility level. The average life expectancy of a new born has increased substantially from 47 years in 1950 to currently 70 years. The UN anticipates a further growth in the next decades to 79 years until 2060 and to 83 years until the end of the century. Whereas a decreasing birth level is slowing down the growth of the population, the increasing life expectancy counteracts this tendency. Both processes – development of fertility and mortality – are accompanied by the ageing of the population. This tendency can be observed in industrial and some developing countries and will play a crucial role in the future for all other countries.