A doublet of immunoreactive bands has been identified in rat liver nuclei, nuclear matrix and lamina by means of a polyclonal antibody against protein kinase C. The two polypeptides show an apparent molecular weight of 77 and 74 kDa on SDS-polyacrylamide gels, and appear to be tightly bound nuclear components, resistant to detergent and high salt extraction. Given the complexity of the genes encoding for protein kinase C, these two forms of the enzyme might be translational products specifically located in the nucleus, involved in the transduction to the genomic apparatus of regulatory signals generated by growth factors and tumor promoters.