Introduction : This thesis is a phonological and grammatical description of Ikposo Uwi, language of the phylum Niger-Congo and Kwa family. It is spoken in Togo by the people Akposso, about 150 000 people that live in the Région des Plateaux. This language divides itself into six dialects : Logbo, Uma, Uwi, Litimé, Ikponou and Amou-Oblo. The study relies on a corpus composed of (i) 36 narratives, (ii) elicitedsentences from picture books, (iii) the lexicon build on these data, (iv) and elicited sentences, generally in connection with the texts. The language used during work session and for translation has always been French.Phonology et tonology : The segmental phonology of Ikposo Uwi (Chapter 1) is quite simple. There are few syllabic schemes and they are not complex. The main characteristic is vocalic harmony, with a 10 vowel system.Ikposo is a tonal language (Chapter 2). Tones are very important on a lexical level, but they encode grammatical informations too. There are four level tones in the Uwi dialect.Morphologie : Nouns and nominal phrases are studied in Chapter 3. Nominal morphology is not very much developed, on the contrary to the rich verbal morphology, with auxiliaries, person index and aspectual prefixes (Chapter 7). Adpositions are studied in Chapter 4 and pronouns in Chapter 5. The other categories are identified in Chapter 6.Syntaxe : The word order is quite rigid : SVOX. This feature is however evolving, as we can see with the yɔ̄ serial verb construction (Chapter 13) that lead to a SOVX word order in some specific discursive contexts.Chapter 8 presents the different enunciative sentence types as well as non verbal predicates.Chapter 9 describes the transitivity and valency system of the language. Modifications in the argument structure are generally not morphologically marked. The only exception is the grammaticalization of 3rd person singular commitative pronoun fà : it makes a transitive-causative construction out fromverbs usually found in intransitive constructions. Ikposo uses massively serial verb constructions. Syntax and types of Ikposo’s serial verb constructions are studied in Chapter 10.The verb dʊ́‘to be at, to put’ (Chapter 11) is one of the most frequent positional verbs, due to its broad meaning. It is also used a lot as V2 in serial verb constructions : with this function dʊ́ undergoes either a grammaticalization process or a lexicalization process. The verb ká‘to give’ (Chapter 12), as V2 of serial verb constructions, undergoes a grammaticalization process, with a global dative meaning.The verb yɔ̄‘to take’ (Chapter 13) is used in serial verb constructions that tend to modify the word order of the arguments from SVO to SOV in some discursive contexts. yɔ̄introduces the object of the main verb or represents it on the main verb. In the latter case, the grammaticalized verb is prefixed yɔ̄-.Chapter 14 gathers the other frequent verbs that do not have a dedicated chapter. Among them, we find lɛ́‘to be, to be at’ used as a copula, bá‘to come’ and ɣā‘to go’ used as deictic verbs, tʊ̄‘to come from’ that grammaticalizes into a prepositional locution, and bā ‘to exceed’ used in comparative serial verbconstructions. Chapter 15 analyses the complex sentences of Ikposo. Among them, completivesare probably the most interesting. They are from two types : build with nominalized verbal predicates or with the quotative nʊ̄, more generally marker of reported speech.Finally, Chapter 16 shows the information structure of the language. I mostly studied the morphological markers of that structure, but a deeper analysis should show that the structure is more complex that these markers let think.