The pace of population growth is slowing down but the immigration flows remain its most important component. The low fertility, the increase of expectancy of life, more rapid among men, and the substantial immigratory flux are the remarkable aspects of the demographic evolution in Portugal.
The fall in the number of marriages and the rise in both the number of wedlock births and the number of divorces confirm the new familiar models in Portugal.
This paper intends to study the patterns of demographic variables responsible for the major changes in both population size and age structure of the population and culminating in its significant ageing.

keywords: population, fertility, infant mort ality, expectancy of life, migrations, ageing