This study shows that utterances ending in an extra-clausal response particle provide interesting evidence in favor of the hypothesis that theme-rheme articulation in Norwegian utterances is grammatically underdetermined. First, a review of the approach used in the study of the functions of Norwegian intonational phrasing is provided. In this approach, the concept of focus is inextricably tied to the appearance of the feature [+foc] in intonational phonology and in surface syntax. [+foc] is a property of intonational phrases (IPs) and their righthand heads, and of syntactic counterparts of IPs called focus domains. In spoken Norwegian conversation, a syntactic element tends to be focused, in the sense of being prosodically highlighted by focal phrase accent, if it is not previously activated in the discourse. From an information-structural point of view, there are two types of unactivated discourse items: there are thematic items setting the frame within which the main prediction holds, and there are rhematic items indicating what is predicted of the item that the speaker has selected as theme. The hypothesis that theme-rheme articulation in Norwegian utterances is gramatically underdetermined, as set forth in this paper, accounts for the absence of a fixed theme-rheme order in Norwegian, and for the absence of other conventional theme-marking, or rheme-marking devices, including fixed intonation contours whose partial function is to separate rheme and theme in an utterance. (VWL)