Since January 1980 a nationwide documentation of childhood malignancies is performed in the FRG. The cooperative documentation system is supported by the Stiftung Volkswagen-werk and centralized at the Institut für Medizinische Statistik und Dokumentation (IMSD) of the university of Mainz. During the first year of the project the incidence of 1002 malignancies has been reported from a total of 62 hospitals with a still increasing number of cooperating centers. The documentation scheme is based on recommendations of the ADT (working group of tumor centers in the FRG) which are in accordance with international recommendations by the W.H.O., U.I.C.C. etc. A newly diagnosed malignancy is reported by a short standardized form to the IMSD which in turn sends out tumor-specific questionnaires of modular structure for obtaining relevant baseline variables. Patient follow-up is achieved by obtaining the status of all patients at least twice a year which is sent in a condensed format to the IMSD. Besides obtaining basic epidemiological data the system will provide detailed analyses on the course of the different malignancies, allow comparisons between different disease groups as well as different hospitals and will serve as a recruiting basis for controlled clinical trials.