The most established experimental model for study of liver regeneration in vivo is partial hepatectomy (PH). Several growth factors and cytokines elicited by hepatectomy have been implicated in liver regeneration. It is now recognized that activation of growth factor and cytokine signalling pathways leads to the induction of cyclin D1, and that cyclin D1 plays a critical role in hepatocyte cell cycle progression. Rodent models for chronic liver disease are often associated with impaired liver regeneration. We found that the expression patterns of cyclin D1 protein correlate positively with the kinetics of hepatocyte DNA synthesis after PH in liver fibrosis and cirrhosis. We will review the role of cyclin D1 in liver regeneration after PH with emphasis on impaired liver regeneration observed in rodent models for chronic liver disease.