This thesis is on the func tional categories of Afaan Oromo based on Chomsky's recentrntheory ( 1993) to ( 1995b). the Minimalist Programme and its subsequent deelopments . Inrnthe thesis an attempt is made to identify different functi onal categories in Afaan Oromornand sho'" their structures in simple clause structures.rnThe thesis cons ists of four chapters. Chapter one deals ,,'ith a brief introduction to thernlanguage and the people. Statement of the problem. objecti"es of the study, thernmethodology used and the significance of the study are also included in this chapter. Therneffo rts made so far to study the language and the a,ailable records of lingui sticrninformation on the language ha"e been discussed. The theoretical frame,,'ork employedrnfor the study is introduced. The o,en'iew of the )!inimali st Programme and the differencernbet"'een the GO'ernment-Binding (GB) and :vlinimali st Programme (MP) Models arernpresented.rnCllJpter t"'o is about the functional categori es of Afaan Oromo, The major functionalrncategorie s such as Pronouns. Determiners. Tense . . -greemenl. :egation. FocLis and Modalrn. .!..u:iliaries hae been ident ified and the ir reali zations are discussed.rnChapter th ree deals " 'ith case, The morphologically realized cases in the language arernidentiti ed, The differen t case markers and case forms are presented , The case markers arernsutti:es such as -ni for nominati"e case, I-f for datie. -nl for instrumental and 1-01 forrnaccus3 ti" e case . In this language. the case markers may appear on both the noun and thernadjecti,'e Which modities them. Structural case is also discussed, Finally. in chapter fourrnthe summary and conclusion are gien.