On African standards, the Kuliak language Ik is one of the few languages with an elaborated case system: Seven cases are distinguished by nominal suffixes. Case is highly productive. Nearly all elements of the language are at least to some extent case inflected: Nouns, adverbs, adpositions, verbs, and even conjunctions. But with core participants (intransitive subject, S, transitive subject, A, and object, O) case marking is defective to the extent that it is even questionable whether case provides a sufficient analysis for the system under consideration. Five case patterns are used to encode the core participants S, A and O. All patterns either show an accusative alignment or no case distinction at all. It will be shown that case is the only reasonable parameter for describing nominal inflection. Ik will be presented as a split (nominative)/accusative language. The core participants are encoded by a complex interplay of head and dependent marking: With core participants the dependent case marking occurs when cross reference by means of head marking devices fails. The language shows a clear distinction between core and peripheral participants. Pragmatically, Ik has a highly grammaticalized focus structure expressed by a separate case marker.