Ribonucleoprotein (RNP) containing structural constituents in hepatocyte nuclei of adult, old and adult, vitamin E-deficient rats were investigated to assess the effect of aging and increased oxidative stress on nuclear functions. Fibrillar centres (FCs), dense fibrillar (DFC) and granular (GC) components of nucleoli as well as perichromatin granules (PGs) in the nucleoplasm were preferentially evidenced by the ethylenediaminetetracetic acid (EDTA) method and measured by computer-assisted morphometric procedures. FCs size and the percentage of nucleolar surface occupied by FCs significantly decreased during aging and vitamin E-deficiency. The percentage of nucleolar surface occupied by GC and DFC remained unchanged in adult and old rats, but in vitamin E-deficient animals GC increased and DFC decreased significantly. PG density significantly changed in aging and vitamin E-deficiency. Functionally, FCs, DFC and GC constitute sites of transcription and processing of ribosomal RNA while PGs are involved in intranuclear storage and transport of messenger RNA. Thus, the present structural changes during aging and vitamin E-deficiency correlate with a decay of nuclear responsiveness to cellular metabolic needs. Considering the antioxidant action of alpha-tocopherol, our data lend further support to the importance of free radical production and control in the aging process.