Treatment of mice with CCl4 and paracetamol induced massive centrilobular necroses. Preliminary induction of hepatocyte proliferation by partial hepatectomy significantly weakened or completely eliminated the toxic action on the liver depending on the time passed after the operation. Practically no damage was observed two days after the operation. Damage of the liver with CCl4 paracetamol and other hepatotoxins is thought to be related to metabolism of these drugs by the hepatocytes and their transformation into toxic substances. In the regenerating liver a reconstruction of metabolism takes place which provides for the proliferative processes. Some tissue-specific functions of hepatocytes, drug metabolizing function in particular, are temporarily lost. This is responsible for nonsensibility of the regenerating liver to the toxins under study.