The cancer registry can be defined as a facility for the collection, storage, analysis, and interpretation of data on persons with cancer. The possible range of registry activities was discussed in relation to the population-based cancer registry. These activities included service to the medical profession and hence the cancer patient, the provision of information for planning control measures, the evaluation of treatment and of screening programs, the conduct of epidemiologic studies, either directly or indirectly, and the education of the public and the medical profession. The resources of the cancer registry can be used in follow-up for industrial and other cohorts exposed to a variety of agents. Registries must be prepared to meet the problem of confidentiality that might arise when information in the registry is linked with other data sets. The value of a cancer registry increases when it becomes possible to examine and assess time trends. Unfortunately, many cancer registries were not adequately funded or staffed to exploit usefully the data already collected at considerable expenses. The three types of staff required to ensure full utilization were discussed.