High levels of salinity often have lethal and sublethal effects on amphibians. In Mexico, salinization is threatening some rivers in arid and semi-arid regions. Here, we report the results of an experiment examining the effects of salinity and density on Pine Toad ( Incilius occidentalis ) tadpoles from the Río El Sabino in the Tecomavaca Canyon in Oaxaca, Mexico. Tadpoles of Incilius occidentalis from Oaxaca were not affected by salinities up to 0.8 ppt in either survivorship or total length. Our results for survivorship and total length are consistent with results from another population of I. occidentalis from the Río Salado in Puebla, Mexico. We found that density reduced total length (i.e., growth) but not survivorship, whereas similar densities did not affect survivorship or size at metamorphosis in the tadpoles from the Río Salado. These results suggest the potential for the existence of differences in the larval ecology of I. occidentalis from these two populations.