In this paper I analyze ergative patterns and the antipassive construction in Matses, a Panoan language spoken in western Amazonia. The Matses antipassive appears initially to be fairly typical, but is unique in that, in addition to the cross-linguistically typical indefinite Patient reading, it can also be used to code an unmentioned first-person Patient. Furthermore, only verbs specifying human O’s can take the antipassive suffix, and only verbs coding significantly affected Patients can have an indefinite reading. This is exactly the opposite of what one would expect of an antipassive construction. This atypical distribution of the Matses antipassive is explained by a combination of interacting factors, including a first-person empathy phenomenon and accommodation to a competing functionally similar object omission construction. © 2006 John Benjamins Publishing Company.