Our previous work with immersive VR indicates that its use during a painful event can reduce subjective pain reports during both acute clinical and laboratory pain by 20-50% [1]. Furthermore, we have shown that effective VR analgesia is associated with reduced pain-related brain activity that is quantitatively and qualitatively comparable to clinically relevant doses of systemic opioid analgesics [2]. The laboratory pain protocol proposed in the current application is identical to the UW HSD-approved protocol used in our previous studies (#25296 - "Reducing Brief Thermal and Electrical Pain"). What is specifically different in the current protocol is the use of naloxone to determine whether VR analgesia operates through an endogenous opioid-dependent mechanism or not. The results of this study will not only suggest the mechanism of action of VR analgesia, but also allow us to more effectively apply immersive VR analgesia in the clinically pain setting through its thoughtful combination with well-established pharmacologic analgesic techniques, such as opioid analgesia administration.