As part of a controlled study with Marines comparing the effectiveness of a predeployment stress inoculation training program against current best practices, the authors have developed a multimedia stressor environment (MSE) for the practice and assessment of stress-reduction skills. The MSE presents a ten-minute scripted scenario of a recon through a Southeast Asian village comprising mission objectives, vehicular and market activity, sudden explosive impact, loud ambient noise, depiction of casualties, post event chaos, presence of insurgents, and other stimuli, and requiring anticipation of enemy engagement, vigilance to in-scene cues, discrimination between normal or expected behaviors and suspicious or dangerous, and multifaceted response. The scenario portrays rendered 3D content projected onto a large surface in a theater-style setup with 5:1 surround sound; hence, any number of combatants can take part, increasing throughput. The rendered content uses scenes, characters, animations, clothing sets, speech, objects, trauma, sounds, and lighting patterns that the authors have developed for past applications. During presentation of the MSE, participants respond to in-scene cues through a game controller, with vigilance and discrimination for specific cue targets. As they respond, cognitive performance (reaction time) and physiologic arousal (heart rate variability) measures are taken to gauge the degree to which participants employ stress-reduction skills. This paper discusses MSE design, development, and testing to include mini-experiments to focus stress-inducing design decisions.