This thesis investigates what forces relate phonological phrases to the syntactic representation, to focus, and to the representation of prominence. The proposal that is defended is that there is a triangle of syntactic constituency, prosodic constituency, and phrasal prominence, in which the grammar places a simple demand on each pair in the triangle: (a) Syntactic phrases must be contained in phonological phrases. (b) Phonological phrases must have edgemost phrasal prominence. (c) Syntactic phrases must contain phrasal prominence. These demands are taken to interact with one another as ranked and violable constraints, where variation among languages is expressed in terms of constraint reranking. Each relation is argued for independently. The effects of (a) (previously analyzed as the role of government in phonological phrasing) will be investigated on patterns of phrasing in the Bantu languages Chi Mwi:ni, Chichewa, and Kimatuumbi. The effects of (b), it is argued, can be seen most clearly in the effects of focus on phrasing, where Chichewa and Japanese will be discussed as examples. The effects of (c), finally, which have been discussed in different contexts as either a directionality parameter of the role of depth of embedding in the assignment of stress, will be argued to have desirable typological consequences that set (c) apart from some of its competitors. Jointly, the constraints will be seen to derive an end-based typology of the kind familiar from work by Lisa Selkirk.