Various road projects have been proposed in the border region of Mexico, Guatemala and Belize, which is part of the Maya Forest, the largest continuous forest in the Americas north of the Amazon. It is also part of the Mesoamerican biodiversity “hotspot,” one of the planet’s biologically richest zones. The Maya Forest is also known for its cultural and archeological riches, having been the cradle of Mayan civilization. The proposals for new road infrastructure are ostensibly aimed at spurring economic growth and reducing the high levels of poverty found in this area. However, the current low density of roads is one of the leading factors that have preserved the Maya Forest’s natural ecosystems. Decision-makers are confronted with an apparent conflict between conservation and development goals. In this study, we analyze the economic and environmental impacts of Maya Forest road projects to enable sound decisions on transportation investments, taking into account their various effects. The study has four elements: 1) Analysis of factors leading to past deforestation; 2) projection of road projects’ contribution to future deforestation; 3) analysis of road’s role in fragmenting jaguar habitat, as a direct indicator of ecological impact; and 4) economic analysis of selected road projects with apparently high likelihood of implementation. The study area covers approximately 100,000 km²of the Maya Forest. Using the analysis of historical deforestation in the region, we modeled the environmental impacts of the following road segments: Caobas-Tikal, San Andrés-Mirador, Mirador-Calakmul, Uaxactún-Mirador, Yaxhá-Nakum-Naranjo, Melchor de Mencos-Arrollo Negro, Lamanai –Border with Guatemala, El Ceibo-El Naranjo and Escárcega-Xpujil (Right-of-way within the Balam-kú y Calakmul reserves for an electricity transmission line of 1 km from the Escárcega-Xpujil road). Our projections indicate that if all the road upgrade and construction projects in this list are carried out, around 311,170 ha of forest would be lost over the next 30 years. This deforestation would release around 225 million tons of carbon dioxide. The global cost of those emissions in present value terms would be on the order of US$ 136 million. By the year 2015, the roads would split six blocks of jaguar habitat into 16 smaller areas, with a total habitat loss of 11.24 percent (151,428 ha) for the species. Fragmentation and easier access to the Maya Forest would increase its vulnerability to fire and hurricanes, and to human pressures such as land appropriation within protected areas, illegal logging and trafficking in wildlife. Further, the road projects would present barriers to the movement of species within and among protected areas, which would seriously undermine the objectives of the biological corridors promoted by the Mesoamerican Biological Corridor effort. The economic analysis was conducted for two projects: Caobas-Arroyo Negro-Tikal; and San Andrés-Carmelita-Mirador. The Caobas-Arroyo Negro-Tikal road would generate losses of approximately US$ 40 million for Guatemala and US$ 14.5 million for Mexico. The San Andrés-Carmelita-Mirador project also showed a negative result, with US$ 21 million in losses for Guatemala. These figures do not take into account environmental costs. Deforestation is estimated at around 53,570 ha for the first road and 36,128 ha for the second. The resulting losses of forest carbon add up to a global cost of US$ 24 million for the Caobas-Arroyo Negro-Tikal road and another US$ 15 million for San Andrés-Carmelita-Mirador. Due to a lack of information, we did not attempt to quantify any other economic losses associated with road-induced environmental impacts. These results suggest that, in fact, there is no conflict between conservation and development goals in the cases of the roads we subjected to economic and environmental analysis. Neither goal would be achieved with these investments since they would cause a net loss of economic resources and provoke considerable impacts on the Maya Forest’s ecosystems. The limited public funds available should be directed to projects with better prospects of satisfying criteria for economic efficiency, environmental sustainability and social equity. In those cases where road projects are already under construction in the Maya Forest, measures are needed to minimize and offset deforestation and to maintain connectivity between natural habitats. This goal can be reached in part through investments in better protection of parks and reserves. In the specific case of the nearly-finished widening of the Escárcega-Xpujil road, there is an urgent need for actions to permit wildlife movement in the Calakmul and Balam-kú reserves, and to locate the proposed hightension electric line adjacent to the road, rather than one km away within the reserves, as has been proposed. This would avoid additional deforestation and fragmentation and would allow for joint mitigation of the road and electric line’s impacts, presumably lowering costs.