DNA synthesis and Nucleolar Organizer Regions (NORs) were studied in C3HS inbred mice standardized for periodicity analysis. Immunohistochemical detection of Bromodeoxyuridine (BrdU) incorporated into DNA with a monoclonal antibody and silver staining of NORs (AgNORs) were assessed by means of a digital image analysis system in histological sections of regenerating liver. Tissue samples were obtained at different times after hepatectomy along a circadian span. The results showed a strong correlation of values between DNA synthesis (BrdU labelling index) and AgNOR numbers, with higher counts during the activity period of animals at 00:00/38 and 04:00/42 hours Time of Day/Hours Post-Hepatectomy (TD/HPH), being the differences with other time points highly significant. Our observations demonstrate the existence of a strong correlation of DNA synthesis measured by BrdU incorporation and AgNOR numbers with a defined circadian rhythm in mouse regenerating hepatocytes.