AbstractFrom the hitherto existing proposals in the literature, no satisfactory explanation has been provided regarding the different sandhi behaviors in such tonal pair as xiaojie ‘young lady’jiejie ‘elder sister’ in Mandarin. This paper attempts to demonstrate through acoustical evidence that accent blocks sandhi, and provide a prosodic explanation to the Mandarin 3rd tone sandhi.The acoustical evidence of the minimal pairs (A) xiaoxiao ‘small’ vs. (B) xiaoxiao (a little boy's nickname) shows that in (A) sandhi occurs, while in (B) no sandhi takes place. This is because the degrees of accent in the first xiao of (A) and (B) differ: the first xiao is more accented in (B) than in (A).Accent and sandhi are incompatible: accent bleeds sandhi. The rules by which accent blocks sandhi are as follows: when the 3rd tone is the right-head of an accent constituent, it does not undergo sandhi; when the 3rd tone is the left-head of an accent constituent or is not at all the head, it undergoes sandhi. However, when this left-headed or not-headed 3rd tone receives a greater degree of accent, it remains unchanged. This prosodic approach provides an explanation to the different sandhi behaviors of the pair xiaojie/jiejie.