This paper considers the notion of split intransitivity as evidenced in the behaviour of perfects in Irish. It is claimed that this language exhibits a distinction between kinds of perfect which roughly corresponds to that between have and be perfects in other languages. However, the choice of perfect is initially somewhat puzzling, and a high degree of variability is found. In response to this, it is attempted to discover if the choice of perfect in Irish is dependent on such semantic factors as agentivity and telicity. The next part of the paper takes the Auxiliary Selection Hierarchy of Sorace (2000) and adapts it to the Irish data. Two semantic groups in particular are investigated: change-of-location verbs and change-of-state verbs. The findings of our examination strongly suggest that semantic factors play a major role in determining the kind of perfect chosen for intransitive verbs, but that one ought to think more in terms of trends in the behaviour of individual verbs, rather than absolute, unvarying rules. The paper tries to come to terms with a typologically unusual body of data. It is hoped that the analysis of this presented below will increase our understanding of the syntax-semantics interface as manifested in split intransitivity.