The time- and dose-dependent uptake of paracetamol into the brain and liver of rats was investigated and correlated with the serum levels of the drug. The results showed a rapid entry of paracetamol into the brain and liver: peak concentration of the drug was reached in these organs at 45 min after oral administration. The concentrations in the brain and liver were significantly higher (P less than 0.01) than in serum. The quick attainment of high concentration in the liver may explain the rapid onset of hepatotoxicity with a single large dose of the drug.