Based on collections and published reports, the herpetofauna of mainland Sonora, México, includes 37 amphibian and 139 reptile species. An additional two amphibian and five reptile species have been taken very near the Sonoran border in contiguous habitats in Arizona, Chihuahua, or New Mexico, and almost certainly occur in Sonora, as well. This compares to 15 amphibian and 95 reptile species documented in the last summary of Sonora's herpetofauna, published in 1945. Five taxa have been introduced, and one species is known to have been extirpated from Sonora. Seventy-three (40%) of Sonora's amphibian and reptile species are given special status under México's Lista de Especies en Riesgo or the IUCN's Red List. Although some of the species probably do not warrant special status in Sonora, substantial threats to amphibians and reptiles in general are widespread. Sonora's sea turtles and ranid frogs are particularly imperiled. Despite these threats, there are significant opportunities for conservation, and agencies and non-governmental organiza- tions are making good progress on several fronts to protect amphibians and reptiles, and their habitats.