Population has become the most specific and important element of any country. Demographical problems are becoming urgent in the world, our Republic is not an exception. Decreasing number of the natural increasment of population is in threatening situation, as the nation appears in danger of extinction. The most we should be worried about is the decreased number of birth. It courses a complicated demographical situation in Lithuania. Moreover it has become unsatisfactory structure of the age, as a result it has become less people, on the other hand the number of able – bodied people is decreasing and the number of elderly is increases. In conclusion the ageing process is developing. The following analyses has been carried out in the paper: 1. The change of number of population 2. Natural increasment of population 3. The dynamic of old age index.