Increases in residual-limb temperatures can occur simply by donning a lower-limb prosthesis and walking. Intrasocket temperatures can also remain elevated long after an activity ends. To address problems associated with activity-related increases in intrasocket temperatures (e.g., discomfort, decreased prosthesis use, lost suspension, residual-limb skin breakdown), an innovative Intrasocket Cooling Element (ICE) system has been developed and tested on ten, transtibial prosthesis users. This report describes the design of the thermo-electric driven, active-cooling ICE system and presents the results of both in-laboratory and at-home testing. Given the capacity for the ICE system to moderate intrasocket temperatures during controlled bouts of in-laboratory exercise, future testing will explore the potential for this technology to reduce the incidence of residual-limb skin issues and improve quality of life outcome measures among a cohort of lower-limb prosthesis users.