This paper provides an account of the behavior of wh-in-situ constructions in Spanish, and argues that the distribution of in situ wh-phrases (non-neutral word order and the Sentence Final Requirement) is governed by phonological properties, not by purely syntactic ones, as in Uribe-Etxebarria (UE) (2002). More precisely, in situ wh-phrases in Spanish need to appear last within their intonational phrase. In order to formalize this idea, Zubizarreta's (1998) formulation of the stress assignment algorithm is taken as the starting point. Then, Stjepanovic's (1999, 2003) system is adopted, a system in which stress assignment and the Copy Theory of movement interact.