This article reports changes in acid and alkaline phosphatases (ACP and AKP), constitutive heat shock protein 70/induced heat shock protein 68 (HSC70/HSP68) and acid and neutral proteinases during liver regeneration (0-144 h) after 2/3 hepatectomy (partial hepatectomy, PH). Both ACP and AKP had two active peaks at 4 and 48 h, 16 and 96 h, respectively, which were followed by significant decrease. The content of HSC70/HSP68 also showed two peaks (16 and 96 h), of which the content after the second peak decreased more obviously than after the first peak. Moreover a 90 kD neutral proteinase was induced at the time from 2 to 6 h and a 27 kD acid proteinase was induced at 36 h. The results suggest that the ACP and the 90 kD neutral proteinase may participate in activating hepatocytes from G0-phase into G1-phase, and AKP and HSC70/HSP68 may play a role mainly in DNA synthesis, cellular metabolism and proliferation. Furthermore 27 kD acid proteinase may be involved in re-differentiation of hepatocytes and reconstruction of liver tissue.