For a long time the molecular basis of nuclear structure has been a matter of debate rather than an established fact. In the last decade the concept of the nuclear matrix has emerged, and the molecular basis of this nuclear infrastructure, although still incomplete, is gradually being unravelled. In early studies concerning the nuclear structure, autoantibodies derived from patients with collagen disease had a significant role. This matrix, the structure remaining after extraction of membranes, nucleic acids and histones, consists of the nuclear lamina, the nucleolus and a fibrillogranular network. The nuclear lamina is composed of the lamins. The nucleolar matrix contains the proteins involved in rRNA processing. The fibrillogranular network is composed of nuclear matrix proteins, a wide variety of which has been discovered. It has become clear that the nuclear matrix not only provides a structural basis for nuclear architecture but also plays a part in regulating nuclear function. Lamins provide mechanical continuity between cytoskeleton and nuclear interior. Aberrant patterns of lamin expression have been described in cancer; these are not sufficiently specific to be used in histopathological diagnosis, however. Nucleolar size and expression levels of nucleolar proteins have been shown to correlate well with proliferative activity, which may revitalize interest in nucleolar organizing regions as a tool in histological diagnosis of cancer. The fibrillogranular network is involved in functional compartmentalization of replication and transcription. A variety of nuclear matrix proteins has been described, which appear to be specifically expressed in cancer cells. Analysis of expression of these proteins might play a significant role in cancer diagnosis.