Knowledge of the range and distribution of species is crucial to our understanding of ecological and evolutionary process- es. Unfortunately obtaining such knowledge for mammals is difficult because it requires extensive time and effort. Indeed it is probable that a complete species list does not exist for any site in the neotropics even for the exhaustively studied Barro Colorado Nature Monument (BCNM) in Central Pan- ama (Voss and Emmons 1996). Here we report the first rec- ord of Alston’s Woolly Mouse Opossum (Micoureus alstoni) from this heavily studied region.