The purpose of the present study was to determine the degree of relationship between neurotoxic chemicals in the blood of chemically sensitive patients and psychoneurological functioning. Blood samples were drawn from 30 patients being treated for environmental illness. All patients were administered a standardized intermediate psychoneurological examination. Results indicate a significant positive relationship between psychoneurological (cognitive neurobehavioral) functioning and the number of and total parts per billion of certain environmental toxins (solvents) in the blood of the subjects. The symptoms most commonly exhibited included deficits in short-term memory, problems with coordination and motor sequencing, somatosensory deficits, and cognitive dysfunction.