The first fifty years of the Connecticut Tumor Registry (1935-1985) have seen unprecedented progress in the collection of standardized data on cancer patients and in the processing of these data, from paper documents to punch cards and magnetic tapes. The need for collecting such information was first recognized, in the early 1930s, by a group of physicians, health professionals, and laymen in New Haven who observed alarming increases in cancer rates and poor survival of cancer patients in this city. This paper recalls the growth and development of the registry and the role played by the Connecticut legislature, the State Medical Society, the Connecticut Department of Health, and the National Cancer Institute in this process. For half a century, the registry has provided assistance to practitioners, hospitals, and research scientists, not only in Connecticut but across the country and around the world. By making available reliable data on incidence and survival, the registry has played a key role in patient management, clinical trials, and etiologic studies. It has also demonstrated the value and served as an exemplary model of a population-based registry. At this juncture in its history, prospects for the future of the Connecticut Tumor Registry appear bright. Its data base will be an essential resource for the recently established Cancer Control Research Unit (CCRU) in the state and for new intervention studies by investigators at Yale, the University of Connecticut, and the State Health Department.