Cerebral blood flow (CBF) was studied in 11 controls and 9 house painters occupationally exposed to organic solvents for a mean of 22 years. They had mild to moderate intellectual impairment, and no or only minor cerebral atrophy was seen in a CT-scan of the brain. The 133Xe inhalation technique was used and the flow was calculated from the initial slope of the 133Xe wash out curve (ISI). ISI averaged 36.8 ml/100 g/min in the painters and 45.4 ml/100 g/min in the controls, representing a significant difference (P less than 0.05). The reduced CBF in these painters with slight to moderate intellectual impairment might be due to limited neuronal loss or to permanently decreased metabolism of the neurones.