In Mexico, as in many developing countries, no monetary estimates of road transport externalities exist. The abundant empirical evidence from the developed world appears to show such research reaching maturity. Yet, several barriers to deriving basic estimates among developing countries persist. In this study, we addressed such difficulties for the Mexican context, and by pooling the available data and using well-established methods, we calculated six categories of estimates. The results showed that road transport externalities amount to at least 59.42 (44.8-73.97) billion US dollars per year or 6.24% (4.71-7.77%) of GDP. By component, accidents represented the largest share (28%), followed by congestion (22%), greenhouse gases (21%), air pollution (13%), infrastructure (7%), and noise (9%). By vehicle type, cars had the highest costs per pkm, and buses had the highest costs per vkm. The costs of road transport externalities in Mexico ranked between those of developed and developing regions, but we found some notable differences when comparing the impacts per pkm of the four largest externalities. We discuss such differences and the policy implications of our findings. We also provide suggestions for future research. © 2013 Elsevier Ltd.