||This paper compares the efficiency of using a standard direct-manipulation graphical user interface (GUI) with that of using the QuickSet pen/voice multimodal interface for supporting a military task. In this task, a user places military units and control measures (e.g., various types of lines, obstacles, objectives) on a map. Four military personnel designed and entered their own simulation scenarios via both interfaces. Analyses revealed that the multimodal interface led to a 3 to 4-fold speed improvement in the average entity creation time, including all error handling. Time to repair errors also was significantly faster when interacting multimodally. These results indicate a substantial efficiency advantage for multimodal over GUI-based interaction during map-based tasks.