One of the missions of the U.S. Army Research Laboratory (ARL) is analyzing the survivability of Army systems in the context of the entire gamut of combat hazards, from ballistic threats like bullets, missiles, and bursting artillery rounds to electronic- warfare threats like jamming and electromagnetic pulses to biological and chemical agents. Because of this role, ARL has an active program of modeling and simulation with a history reaching more than 50 years back through a predecessor organization, the Ballistic Research Laboratory (BRL), all the way to ENIAC. Over the past decade, as Tcl/Tk has developed, we have adopted it for integra- tion into our existing applications with great success. In this paper we discuss the problem domains, our software practices before Tcl/Tk, the extent and nature of our incorporation of Tcl/Tk, lessons that we have learned, and our plans for future efforts.