Studies of sentence comprehension in different languages have enhanced our understanding of how syntactic and semantic information are used in interpreting sentences. However, few studies have attempted to assess how such information affects sentence-processing speed. The present study explored effects of case inflections, gender agreement, noun animacy, and word position on decisions and reaction times for, agent-object assignment in Croatian, a case-marking language with a rich grammatical morphological system. In accordance with Bates and MacWhinney's Competition Model, results provided evidence that the various cues to agent-object relations converge and compete to affect not only agent-object decisions, but also the speed with which those decisions are made. However, several findings from the present study did not support predictions made by the Competition Model. For example, cue strength (i.e., the relative weights that listeners assign to cues) was not a good predictor of reaction time for agent-object assignment in the present study. In addition, reaction times were not always shortened by converging information or inhibited by competing information – both of which were predicted by the model. Rather, our results support the view that, in a given language, there may be constraints on the particular combinations of cues which may converge to facilitate, or compete to inhibit, agent-object assignment. The pattern of cue interactions, which was obtained for the response latencies of normal adults in the present study, is similar to that revealed by off-line choice data from a group of Croatian aphasics (Smith & Bates, 1987), another situation in which ceiling effects of the dominant case cue were removed; thus, these results may tap into a basic aspect of the human sentence processor.