This exploratory research addressed the retrofit of existing licensed nursing home wings into special care units for Alzheimer's disease patients. This type of unit was coined Alzheimer's Care Unit (ACU). This research compared the retrofit design and lighting characteristics of ten Texas ACUs to Alzheimer's disease patient wandering. A facility questionnaire, site observations, behavioral mapping, illumination readings, and field notes were used to gather and compare resident wandering and environmental characteristics. Illumination levels were measured and compared to the Texas Department of Health's minimum requirements for licensed nursing homes. A ranked, lighting evaluation was developed regarding code requirements, fixture type, placement, and safety. The findings revealed that through careful ACU retrofit design the impact of Alzheimer's disease to the victim and the caregiver can be ameliorated. The initial retrofit design decision of public areas and the nursing station placement in the ACU dramatically affected professional staff workloads, efficiency, and resident behavior. Behavioral problems were exacerbated by design decisions to change, remove or maintain certain environmental features, particularly lighting. Seventy percent of the retrofitted facilities did not meet the minimum required light levels of 20 footcandles in the corridors, all failed to meet the minimum levels in toilet areas, and 20% had improperly positioned luminaires. Resident exposure to direct or indirect sunlight was dependent on professional staff decisions; rarely did direct sunlight enter the ACU and if so, only in locations or times when residents could not access these areas. Unique behavior observations indigenous to Alzheimer's disease were compared to the applicability of current design codes and regulations. Specific ACU retrofit lighting and ideal retrofit guidelines were developed. Recommendations for further environmental research were discussed.