本文討論台灣閩南語元音系統及陰、陽入聲調的變異與變化，我們根據近三年台灣閩南語的字表調查，運用音韻對稱以及分散理論分析台灣閩南語元音系統的變異與變化。台灣通行腔閩南語的/i、e、a、u、o、ɔ/六元音系統，結構不對稱平衡，/o/、/ɔ/過於接近、不易辨識。因此兩種優勢元音系統正在形成、擴張，一個是南部/i、e、a、ə、u、ɔ/的六元音系統，一個是[o]、[ɔ]混同為一的五元音系統。而台灣閩南語陰、陽入單字調會因為韻尾不同呈現不同的變化趨勢。喉塞尾的陽入單字調有的維持本有的陽入調，有的則讀為中長調[33]，或讀同陰入的中短調[32]，其中最優勢的變體是讀中長調[33]，有的方言點前述兩種或三種變體兼而有之；至於[-p]、[-t]、[-k]的陰、陽入單字調，也有部分的混同現象。文中並以鹿谷方言的實證調查，描述該方言陰、陽入單字調混同的趨勢。本文的主要貢獻有：(1)從較新的調查資料，找出台灣閩南語元音系統演變的兩個類型，即南部六元音系統及[o]、[ɔ]混而為一的五元音系統。(2)釐清不同韻尾陰、陽入單字調的變異與變化，描述分析陰、陽入單字調變化詞彙擴散的動態過程。

This study aims to probe the vowel system change and the Yin-/Yang-entering monosyllabic tonal variations in Taiwanese Hokkien. In the first part, we analyze the variations of the vowel system in Taiwanese Hokkien by means of a wordlist investigation into eleven dialects in this language, and bring forth variational rules as accords phonological symmetry and adaptive dispersion theory. Our research tells that there exists asymmetry in the six-vowel system /i, e, a, u, o, ɔ/ by the fact that /o/ and /ɔ/ as two vowel systems are too close to be distinguished from each other. This fact results in an on-going divergence of two prestigious variations. One refers to a six-vowel system that we are having particularly in Tai-nan and Kao-hsiung, and the other refers to a five-vowel system where /o/ and /ɔ/ might merge into one in such areas as Da-niu-lan and Jen-tse. In the second part, we find that different codas consequentiate different realizations of the Yin-entering and Yang-entering monosyllabic tonal variations. With a glottal stop, a monosyllabic Yang-entering tone tends to become a mid-long one in some dialects, while it can also become a mid-short tone as in the case of a Yin-entering one in other dialects; still in other dialects, the two tonal variations happen to coexist. When the coda is [-p], [-t] or [-k], sporadic mergence happens between Yang-entering and Yin-entering tones. To sum up, this current study contributes both to finding two subtypes of the vowel system change in Taiwanese Hokkien, and to clarifying the way in which the Yin-entering and Yang-entering monosyllabic tonal variations are realized as the coda varies dynamically with its lexical diffusion in this language.