In only 12 years, from 1987 to 1999, world population increased from 5 to 6 billions. In the last years its growth has diminished, both in a relative way, and in a absolute way, due to a reduction in fertility faster that the one expected in the last years. Nevertheless, great differences between areas and nations exist; the poorest countries are the ones in which the growth is more extreme.The predictions of world population reaching 9–10 billions at the middle of (...) the next century could come true, followed by a stabilisation; the danger of an uncontrolled growth of the world population would be, in this way, avoided. The question of the credibility of these predictions, and of which alternatives can exist, belongs not only to the scientific debate. As it happens in social and economical planning, ethical choices, which in this case are definitely appointed to the peaceful cohabitation between nations and to their maximum welfare, must be faced. The debate will focus on how to reach them. (shrink)