This paper provides an in-depth examination of the distribution of the Antipassive morpheme -si- in Mittimatalik, a dialect of !nuktitut spoken in North Baffin. It is demonstrated that the occurrence of the overt Antipassive marker in Mittimatalik correlates with the argument structure of the verb. The analysis of the Antipassive takes into account the fact that only inherently transitive verbs and causativized verbs require the Antipassive marker in the Antipassive construction. It is proposed that the Antipassive morpheme -si- occupies v and is responsible for accusative assignment to the patient argument. Assuming that v is the focal point of transitivity, the differences in argument structure lie therefore in the feature make-up of v....