This paper argues that case assignment to indirect objects in Icelandic is determined by theta-roles in that recipient and benefactive indirect objects are always assigned dative case. Indirect objects with accusative case are neither recipients nor benefactives. The association between dative case and recipients or benefactives holds for direct objects and subjects as well as indirect objects.
Nominative subjects which seem to be counterexamples are argued to have some agent properties which prevents them from getting dative case. The idea is independently motivated by the fact that all ditransitive verbs in Icelandic have nominative subjects even if some of these subject are not agents in the usual sense of that word.