Abstract: This paper studies how focus,lexical stress and rising boundary tone act on the fundamental frequency(F0) of the immediate preboundary word of intonational phrases based on two American English corpora.The results show that when the preboundary word is focused,the F0 peak of lexical stress is even higher than the F0 height required by the rising boundary tone at the end of the word.Boundary tone is represented after the realization of this focus.Furthermore, the location of lexical stress in the syllable structure can be a key factor to restrain the post-focus pitch range.When the preboundary word is non-focused,the rising boundary tone takes control almost from the beginning of the word and flattens the F0 peak of lexical stress.Our conclusion is that each prosodic feature has its best functional realization at a particular stretch.Focus can be realized by lifting the F0 peak of lexical stress;and the strength of realization of focus and boundary tone is limited by the location of lexical stress in the syllable structure,and under extreme conditions boundary tone is only carried by the last part of the immediate preboundary syllable.This interaction of focus,lexical stress and rising boundary tone on a single word thus leads to the F0 competition due to limited articulatory dimensions.