This dissertation is a study of certain clause-level constructions: in the Okanagan language and. an exploration of the adequacy of Relational Grammar for describing these constructions. Four major issues are addressed: (i) the nature of transitivity in Okanagan; (ii) the identity of the grammatical relations which are necessary to the syntactic analysis of Okanagan; (iii) the occurrence of re-evaluations of these grammatical relations in this language; and (iv) the nature of the Middle voice in this language. Arguments and language, data are brought to bear on these issues, providing evidence to support (1) the characterization of transitivity as a property of strata or level rather than of clause or of verb; (ii) the necessity in Relational Grammar of the grammatical relations: Subject, Direct Object, Indirect Object, Dative, Instrumental, Locative, Topic, and Chomeur for the syntactic analysis of the language; and (iii) the occurrence of the following re-evaluations: 21 Advancement and 11 Demotion in Passive constructions; Phantom Advancement of a non-nuclear object, non-distinct with the initial subject; Unaccusative Advancement; Dative, Locative, Relational and Instrumental Advancements, with concomitant Demotions of the nominal previously bearing the target relation; and Possessor Ascension; and (iv) a Phantom Arc solution for the syntactic analysis of the Middle, voice, construction in this language. It is concluded (a) that, the analyses presented contribute in an explanatory way to the study of Salishan linguistics; (h) that these analyses attest to the productivity of the theoretical model, Relational Grammar, with, respect to certain clause-level constructions of Okanagan; (c) that some rules referring to transitivity require reference to non-distinctiveness as well as to 1 and to 2; (d) that one of the principles of Relational Grammar, the 1-Advancement Exclusiveness Law, must be modified to allow language-particular conditions: on its applicability; and (e) that the theory of Relational Grammar needs further elaboration to deal with the mapping of thematic relations onto grammatical relations. / Arts, Faculty of / Linguistics, Department of / Graduate