In the 2001-2008 period Portugal experienced a continuous growth of the population, at a weak and decreasing rate. This growth results almost exclusively of the net migration, since the natural change is very low, becoming even negative in 2007. Fertility remains at levels far below those necessary to renew the generations, longevity increases, and both these factors intensify the process of demographic ageing.
The new family models in Portugal are the result of the significant fall in the number of marriages and the strong rise of the number of wedlock births, the number of divorces and the average age at marriage.
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, mortality, expectancy of life, migrations, ageing.