As part of a recent project on the distribution and status of primates (Ateles geoffroyi and Alouatta palliata) in the tropical forests of northeastern Oaxaca, Mexico, we report the presence of spider monkeys (A. geoffroyi vellerosus) in a tropical dry forest south of the Isthmus of Tehuantepec, Oaxaca, Mexico. During March and May 2003, we documented the presence of spider monkeys at 5 sites (2 direct observations and 3 indirect records based on vocalizations, presence of feces, and a carcass). The presence of spider monkeys in a landscape dominated by tropical dry forest suggests that this species has an ability to inhabit a broad range of tropical forest types. Two factors threatening the continued presence of monkeys at these sites are increasing forest destruction as a result of highway construction, and hunting and capture for the pet trade.