We describe immunofluorescence detection of the vimentin epitope, recognized by monoclonal antibody VI-01, in chromatin structures of eukaryotic cell nuclei and chromosomes. The approach used is based on increased sensitivity of 5-bromodeoxyuridine (BrdU)-substituted DNA to UV irradiation-induced crosslinking of DNA with proteins in vivo, by which the proteins interacting with chromosomal DNA can be immunovisualized in situ.