This is a hierarchical decimal classification of information related to cancer biochemistry, to host-tumor interactions (including cancer immunology), and to occurrence of cancer in special types of animals and plants. It is a working draft of categories taken from an extensive classification of many fields of biomedical information. Because the classification identifies very small areas of cancer information, it can be used for precise matching of cancer researchers with useful documents or data in information systems, and for detailed analysis of large cancer research programs. (ED 025 270 and LI 004 018-LI 004 019 are related documents.) (Author)