This paper presents results of the first quantitative phonetic study of Koasati, a Muskogean language spoken in Louisiana and Texas. We examine vowel quality, length contrasts in vowels and consonants, the limited system of lexical tone contrasts in nouns, and the grammatical system of tone in verbs. We also study the realization of several word-final consonant clusters (fn, tl, lw, etc.) that are absent in related languages and that are typologically unusual due to their sonority reversals. Finally, we examine the cognates in related languages of the tones we document in Koasati nouns and verbs
