The prognosis of chronic toxic encephalopathy in former house painters was examined in a prospective study with a two-year observation period. Twenty-six patients, who at the initial examination had cerebral atrophy and/or intellectual impairment, were selected for the follow-up study. No competitive etiological factors (including alcohol) to the encephalopathy were suspected. During the two-year follow-up interval these patients were not professionally exposed to organic solvents. At the follow-up examination neurological, biochemical, neuropsychological, and neuroradiological parameters were reassessed and compared to the original findings. Generally the condition was unchanged. Slight improvements with regard to headache and dizziness were reported by some. However, the neurological status, the neuropsychological impairment, and the cerebral atrophy, did not change significantly. In three patients further deterioration was observed. It is argued that our patients suffered from a brain disorder different from presenile dementia of the Pick-Alzheimer type. Other alternative etiological entities were also excluded. Our findings indicate that long-term exposure to organic solvents may lead to a chronic brain syndrome. Once intellectual impairment and/or cerebral atrophy had developed, reversibility is not observed. Nor is further progression to be expected if exposure is stopped. Occupational exposure to organic solvents should be maximally restricted as it represents a risk of inducing invalidating brain syndromes.