An assortment of road projects has been proposed in the border region of Mexico, Guatemala and Belize, which is part of the Maya Forest, the largest contiguous tropical forest in the Americas north of the Amazon. The proposals are apparently aimed at spurring economic growth and reducing the high levels of poverty found in this area. But more and better roads usually bring more people and expand farms. Decision-makers are therefore confronted with a seeming conflict between conservation and development goals. Would new roads be bad or good for the Maya Forest region? To help answer that question , we analyzed the economic and environmental impacts of proposed road construction and improvement investments. Economic returns to Guatemala and Mexico were calculated for two projects that would join the two countries through currently roadless forest of the Maya Biosphere Reserve. Deforestation , habitat fragmentation and forest fire were projected for a larger set of projects. We used two separate models to predict these impacts, one focused on just Guatemala's Maya Biosphere Reserve, and the other looking at a larger, three-country area. Our projections indicate that if all the projects in this list are carried out, as much as 311,000 hectares (769,000 acres) 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. A lower-bound estimate for deforestation in the Maya Biosphere Reserve alone is 37,500 hectares, obtained with a more conservative modeling approach.