This article argues for the hypothesis that the location of the nucleus of the intonation contour is rule-governed. The term ‘nucleus’ is taken to refer to what has elsewhere been discussed as the ‘nuclear syllable’ (Crystal, 1969), ‘tonic’ (Halliday, 1967a), ‘sentence stress’ (Schmerling, 1976), ‘[I stress]’ (Chomsky & Halle, 1968), and ‘Designated Terminal Element’ (Liberman & Prince, 1977) (ignoring certain differences of analysis, such as that between double-nucleus and single-nucleus interpretation of some contours). Drawing on the facts of English and Dutch, it does so by attempting to identify the linguistic options available to speakers that are relevant to the location of the nucleus. The main argument hinges on the assumption that the chief functions of the location of the nucleus are (1) to signal the focus distribution of the sentence and (2) to signal whether the sentence is or is not meant as a counter-assertion, with the proviso that in many instances the location of the nucleus allows of more than one interpretation of one or both variables. Section 1 devotes some discussion to the problem of predictability, while the concepts of ‘focus’ and ‘normal stress’ are explored in Sections 2 to 4. Section 5 states the sentence accent assignment rule (SAAR), giving illustrations of its application. In Section 6, special attention is devoted to the pragmatic effects of SAAR in subject + predicate sentences. Section 7 attempts to give a fuller definition of the constituents the rule refers to and puts a general condition on its application. Section 8 introduces the variable mode, while Section 9 defines the problem of the location of the nucleus in sentences with minimal focus and introduces another accent assignment rule (PFR). A summary in the form of a set of propositions concludes the article. I should like to point out that most of the examples in this article are attested; it is only the more pedestrian ones that have been made up for the purpose of illustrating certain points.