During the early liver regeneration following partial hepatectomy, distinct changes of the transcriptional activity of hepatocyte nuclei are observed. Changes in the proportion of dense fibrillar component (DFC) and granular component (GC) of nucleoli are related to pre-rRNA synthesis. The RNase-gold ultracytochemical method was applied to localize RNA molecules in thin sections of regenerating rat liver hepatocyte nuclei. The method allowed for the detection of pre-rRNA molecules at the periphery of fibrillar centers (FC). The distribution of colloidal gold-RNase complexes in combination with quantification of labeling density demonstrated the highest transcriptional activity of nucleoli 18 hours following partial hepatectomy.