This paper analyzes middle voice expressions in Pima Bajo, a Uto-Aztecan language spoken in northwest Mexico. The analysis shows that the reflexives and middles differ in that in the latter there is no coreferential relation among the participants. It also shows that middles differ from reflexives in the semantic role of the subject participant: agent in reflexives and executor or patient in middles. Pragmatic factors condition the semantic role of executor. © 2005 by The University of Chicago. All rights reserved.