The purpose of the present study was to ascertain if environmentally sensitive patients would demonstrate different memory deficit patterns than psychiatric patients on objectively measurable memory tasks. One-hundred sixteen patients were surveyed; 56 environmentally sensitive patients were compared to 60 psychiatric patients. All subjects were administered a Wechsler Adult Intelligence Scale-Revised screen, the Wechsler Memory Scale-Revised and the Harrell-Butler Comprehensive Neurocognitive Screen after history of head injury was ruled out. Results indicate a significantly different pattern of memory dysfunction between the environmental patients and the psychiatric patients, indicating two different etiologies. A screening device derived from the coefficients from a Canonical Analysis is proposed to distinguish between the two populations in the absence of blood serum levels of environmental toxins or poisons. The detrimental effects of misdiagnosis and the beneficial effects of accurate diagnosis of environmental illness are discussed.