Introduction: The risk of transmitting HIV from mother to unborn child, without prophylactic intervention, is 30% but can be reduced to less than 2% by implementing comprehensive preventive strategies. The objective of this study was to assess the epidemiological profile of vertical HIV transmission in the Southern Cone (Argentina, Bolivia, Brazil, Chile, Peru and Uruguay). Material and methods: We analyzed data obtained from the Epidemiology Departments of UNAIDS, WHO and the official Government Health Departments and institutions of the above-mentioned countries up to 2006. The study included assessment of infection rates in the general and fertile female populations, the prevalence among pregnant women, and vertical transmission rates. Results: The prevalence of HIV in the Southern Cone in 2005 was 60 per 100,000 inhabitants in the general population, 32% of which corresponded to women of fertile age. The predominant subtype in the region was HIV-1 B and the gender ratio (male:female) was 3.15:1. Among the female population, the highest HIV infection and AIDS rates were observed among those in the groups aged 15-24 years and 30-39 years, respectively. The mean global fecundity rate in the region was 2.3. The infection rate for the fertile female population ranged from 65 to 370 per 100,000. The mean infection rate in pregnant women was 0.5% and the mean vertical transmission rate was 3%. Conclusions: Vertical HIV transmission in the region causes a small percentage of HIV/AIDS notifications, but accounts for approximately 92% of the infected children. This route of transmission route has decreased substantially, reaching prevalence rates of less than 2%, which may be explained by the wider use and effectiveness of the health policies implemented by governments and health organizations for the prevention and treatment of this infection. © 2009 Sociedad Española de Ginecología y Obstetricia.