The term loch tuile is not recorded in published lexicographical sources for the Irish language, but is used to refer to pulmonary ailment in Irish medical ma- nuscripts copied during the fifteenth and sixteenth centuries, in one case oc- curring as an interlinear gloss on the Old Irish legal text known as Bretha Déin Chécht (‘The judgements of the [mythological physician] Dían Cécht’). This contribution will examine some attestations of this term and its derivatives from the corpus of unpublished Irish medical tracts, with the dual aim of shed- ding further light on the technical terminology of medieval Irish medicine, and of offering some preliminary observations regarding the relationship between texts extant in four separate medical manuscripts.