This article offers a theoretical and empirical review of the main factors that have exerted strong influence in the demographic composition and transition in Colombia. Among the variables considered are fertility, mortality, epidemiologic change, health coverage, change in age patterns and migratory flows. A reduction of the fertility rate in 65% in just 50 years (1951-2005) is observed; on the other hand, thanks to health conditions within which people are born and live, life expectations after birth have increased to 72.2 years, and the mortality rate has decreased to 68%. Likewise, epidemiologic change and health coverage have produced a change in mortality according to age within the population. As to migratory flows, it is worth to pinpoint that the most important cause of spontaneous movements is the growing disparity of development levels within and between coun