We describe a perceptual experiment whose goal is to compare perceptual sensitivity to pitch accent contrasts in nuclear and prenuclear positions. The material consists of Czech sentences which have been resynthesized with controlled intonation. The results show that changes in nuclear pitch accents are perceived more sharply than changes in prenuclear pitch accents, and that the H. accent is perceptually more salient than the other accent types (L.H, L. and S.). The effect of constituent edge on the perception of intonational contrasts has not been confirmed.