The border area between Brazil, Colombia, and Peru has a population of over 100,000 people; at least a quarter are indigenous (mostly Tikuna), and the rest is composed of people from the Andean region and some itinerant groups (migrants, traders, etc.). The “twin cities”, Tabatinga (Brazil) and Leticia (Colombia), receive a significant flux of people from the adjacent regions of each country, each one having a referral hospital for attending cases of moderate complexity. This region has a high incidence of  water-borne diseases, such as diarrhea and hepatitis, those transmitted by vectors, such as malaria and leishmaniasis, and other infectious diseases related to living conditions and the level of access to the health system, such as sexually transmitted infections, tuberculosis, and Hansen’s disease.. This work presents attempts to carry out a global analysis of the prevalence of some health problems introduced into the area during the last two decades, such as cholera epidemics, malaria, and HIV/AIDS infection, attempting to describe their main determinants in the region.