This chapter gives an analysis in the framework of Bidirectional Optimality Theory (BiOT) of the relationship between nuclear accent and focus. Nuclear accent is a pitch accent that occurs near the end of an intonational phrase. Optimality Theory ( OT) makes use of a limited number of soft constraints (violable principles) ranked according to their relative strength. Optimal solutions are searched along two dimensions: (i) the dimension of the speaker who compares different prosodic forms for one and the same focal structure to be communicated; and (ii) the dimension of the hearer who compares different focus interpretations for a given prosodic form. The chapter analyses a number of illustrations of optimisation procedures involving the choice of nuclear accent/focus pairs for a given context. The constraints illustrate the interaction between syntax, semantics and pragmatics in determining the placement of accent within focus constructions.