The classification may be used (1) to identify cancer research efforts supported by NCI in selected areas of research (at any general or specific level desired), (2) to store information related to cancer research and retrieve this information on request, and (3) to match interests of cancer research scientists against information in published articles so that scientists can receive copies of articles specifically related to their research (Selective Dissemination). The outline of major categories for cancer research information is as follows: 51.1 Selected general topics related to cancer research, 51.2 Clinical aspects of diagnosis and treatment, 51.3 Pre-clinical aspects of diagnosis and treatment, 51.4 Cancer epidemiology, etiology, carcinogeneses, 51.5 Cancer pathology, related physiology, cytology, and tissue culture studies, 51.6 Biochemistry of tumors and tumorbearing hosts, 51.7 Host-tumor interactions, and 51.8 Cancer in specific types of host. (Author)