We analyzed museum specimens from two regions of Guatemala for the presence of the pathogenic amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) using both histological and PCR-based assays. We determined that the pathogen was present at one site at low prevalence in 1980 and 1981, immediately preceding drastic declines of amphibian in the region by 1983. This pattern is consistent with pathogen-driven declines of amphibians in other regions of Central America, suggesting that Bd was the primary cause of amphibian declines in the Sierra de las Minas of east-central Guatemala.