A computer data system by which data from radiation therapy records are stored, corrected, and up-dated continuously as information becomes available is described. Two main programs are involved. A data storage and retrieval system called TAXIR uses a high-level language similar to English and allows display of information in alphabetic or numerical fashion. The other program, MIDAS, is a statistical package designed to perform multiple statistical analyses on the data accumulated on the former program. Both of these programs utilize a logical syntax permitting easy identification and partition of a data set. In addition, several smaller program have been developed to advance survival information in a rapid and reliable way and to obtain information directly from computerized data available at the University of Michigan Cancer Follow-Up Unit. Programs to obtain life tables or graphs on survival or reactivation of neoplasms have been developed. Stress is placed on the development of a strategy to obtain the maximum accurate information with a minimum input. The development of suitable coding sheets including appropriate diagnoses and tumor classifications is discussed. The importance of keeping a continuous up-to-date flow of information is stressed.