Infrared thermography has been recently proposed as an access technology for individuals with disabilities, but body functions and structures pertinent to its use have not been documented. Seven clients (2 adults, 5 youth) with severe disabilities and their primary caregivers participated in this study. All clients had a Gross Motor Functional Classification System (GMFCS) level of 5, but each possessed a unique set of extant physical movements. We tested the clients' ability to activate the infrared thermal access technology via a cued mouth open-close exercise. In addition, the clients or their primary caregivers were interviewed for descriptive information about the clients' physical, cognitive, and sensory function; communication skills; medical background; and history of switch use. Several impairments were identified as contraindications to infrared thermal access, spanning physiological (e.g., frequent fluctuations in body temperature, seizures, pain), motor (e.g., poor trunk control, involuntary movements, atypical mouth posture), and sensory/cognitive (e.g., inconsistent contingency awareness) subdomains. We identified key impairments in body functions and structures that limit infrared thermography-based access. Potential changes to the access technology (e.g., software and hardware) and physical environment to overcome those limitations are suggested. (Contains 2 figures and 4 tables.)