This presentation details a case study of two competing participles of the Spanish verb matar ‘to kill’ (matado/muerto ‘killed/dead’). I provide quantitative data from corpora of modern Spanish that show that muerto ‘dead’ is the preferred form for matar in passive periphrastics. The use of the participle muerto (from the infinitive morir ‘to die’) in the paradigm of matar has long been considered a textbook example of verbal suppletion in Romance; however, I offer an alternate explanation. The objective of this analysis is to demonstrate that these two participles are best considered to be allomorphs of the same archimorpheme /to die/. The general premise of my claim is that agentivity determines the distribution of forms: an agentive reading triggers the participle matado, while a non-agentive reading triggers muerto. The nature of this particular instance of verbal allomorphy provides insight into the origins and maintenance of irregular verbal forms in language.