Administration of CCl4 and paracetamol to mice causes massive necrosis of the central regions of the hepatic lobule. Preliminary stimulation of hepatocyte proliferation by partial hepatectomy greatly reduces the intensity of the toxic effect or abolishes it completely, depending on the time elapsing after the operation. The liver was virtually insensitive to hepatotoxins 48 h after the operation. Damage to the liver by CCl4, paracetamol, and other hepatotropic poisons is associated with conversion of these compounds by the liver cells into toxic metabolites. In the regenerating liver metabolism is reorganized in favor of proliferative processes. Some tissue-specific functions of the hepatocyte are temporarily lost under these circumstances, notably the ability to metabolize foreign substances; this explains the resistance of the liver to hepatotoxins.