The concept of health transition is considered to include two interrelated processes: transition of health care and epidemiological transition. The latter encompasses three basic processes: (a) replacement of the common infectious diseases by noncommunicable diseases and injuries as the leading causes of death; (b) a shift in peak morbidity and mortality from the young to the elderly; and (c) change from a situation in which mortality predominates in the epidemiological panorama to one in which morbidity is dominant. Latin America is characterized by a heterogeneous health profile in which different countries are in various stages of epidemiological transition. However, in most of them, the transition experience is unlike that of the developed countries and is distinguished by: (a) a simultaneous high incidence of diseases from both the pre- and post-transitional stages; (b) a resurgence of some infectious diseases that had previously been under control; (c) a lack of resolution of the transition process, so that the countries appear to be caught in a state of mixed morbidity; (d) a peculiar epidemiological polarization, not only between countries but also in the different geographical areas and between the various social classes of a single country. This experience is called a "prolonged polarized model."