This supplement presents the study of various histologic types of cancers diagnosed in the populations covered by the Surveillance, Epidemiology, and End Results (SEER) Program. It describes the SEER program and the coding of histologic type by the International Classification of Diseases for Oncology. Each of the 19 articles deals with the histologic types of cancer found in major sites or with specific histologic types, such as lymphomas or melanomas. Histologic types have been grouped based on those developed by Dr. John Berg. Data presented in this supplement are based on more than one million microscopically proven invasive cancers and 98,000 in situ cancers diagnosed during the period 1973-1987 in areas covered by the SEER Program.