Abstract : This article focuses on the prosodic organization of Shǐxīng, a tonal Sino-Tibetan language spoken in the South-West of China. It is essentially based on an experiment that explores the derivational relationship between the three contrastive tones on monosyllables, /H/, /L/ and /HL/, and the three contrastive tones on phonological words of two syllables or more, likewise /H/, /L/ and /HL/. The process of tone derivation in phonological words of two syllables or more is determined by the presence or absence of lexical tone on the initial element of the phonological word (a morpheme or a word) as well as by the length and composition of the phonological word. The observed phenomena of tone derivation are here explained under the assumption that a prosodic domain in Shǐxīng is characterized by metrical stress, which is the location for the insertion of either of the three lexical tones. The default location of stress is domain-initial. The lexical tone of a stressed syllable in initial position spreads onto the remaining syllables, followed, in the case of the lexical /L/ tone, by the addition of a postlexical [H] tone. In tonal domains that begin with a toneless syllable (e.g. prefix or proclitic), stress is shifted to the first stressable syllable to its right; the contrast between /L/ and /HL/ neutralizes to /L/, while /H/ remains unchanged. When the first stressable syllable is two syllables apart from the domain-initial position, all three tones are neutralized to /L/.