This paper describes the concurrent design of a wearable computer, called the Navigator, developed and built at Carnegie Mellon University in a multidesigner, multidomain environment, The design effort for the Navigator involved nineteen designers, representing the disciplines of electrical engineering, industrial design, mechanical engineering, software engineering, and human-computer interaction, The concurrent design framework developed by the Navigator design team is outlined and the parallel activities within each design phase are described, including the syncronization and interactions among all design disciplines at the phase boundaries, The evolution of the interdisciplinary design of the Navigator wearable computer is presented, with particular emphasis placed upon the role of the thermal design group in the overall design process; Furthermore, the particular challenges associated with the concurrent thermal management of wearable computer systems are outlined.