This PhD research aims at a systematic and corpus-driven study in Luganda of how the modal core concepts of possibility and necessity are expressed, along with closely related categories, such as volition and evidentiality. Special attention is paid to the role of grammaticalization in the emergence of modal markers in Luganda, i.e. how independent lexical morphemes pertaining to the objective world evolve into grammatical morphemes or function words whose syntactic status becomes increasingly less autonomous (Heine et al. 1991; Bybee et al. 1994; Hopper & Traugott 2003). It is also examined how grammaticalization in the structural domain correlates with ‘subjectification ’ in the semantic domain, namely the semantic evolution from ‘objective’ meanings based in the outside world to meanings which ‘tend to become based in the speaker’s subjective belief state / attitude toward the proposition’ (Traugott 1989: 35).