OBJECTIVES: The United Nations is setting country-by-country targets for universal access (UA) to antiretroviral treatment for persons with HIV/AIDS. This study attempts to estimate the relative economic affordability of UA targets in 20 Latin American countries. METHODS: HIV/AIDS prevalence and antiretroviral treatment rates for 20 Latin American countries were obtained from a 2006 UNAIDS report. Two UA targets were estimated for each country: (1) 100% of all HIV-infected patients, and (2) 83% (the estimated rate of Brazil's established UA program). National budget expenditures (in 2001 to 2005 U.S. dollars) for HIV/AIDS and for overall health spending were also obtained from UNAIDS. The additional budget expenditure required to meet the UA targets was estimated by multiplying the number of currently untreated patients by the per-patient budget expenditure for each country. Ratios of the budgetary changes to national income and to overall health care spending were calculated to measure each country's relative ability to pay for the increased access to treatment. Sensitivity analysis was performed on all inputs. RESULTS: For 83% UA, an additional 1.1 million patients require treatment, and on average, each country must increase its rate of access by 28% (ranging from 2% in Argentina to 67% in Nicaragua). On average, HIV/AIDS budget expenditure per capita needs to increase by 60% from $1.53 to $2.46 to meet the 83% target. Five countries (Belize, Honduras, Nicaragua, Paraguay, and Suriname) would be required to more than double there rate of HIV/AIDS spending, and 10 countries would need to spend a higher percentage of their national income on HIV/AIDS compared to Brazil. These results increase substantially for the 100% target. CONCLUSION: Several Latin American countries, particularly countries with smaller populations, may be required to increase HIV/AIDS expenditures substantially in order to meet these UA targets. Many countries may have more difficulty affording the targets compared to Brazil.