This study was initiated in 1957 by the U.S. Public Health and many facets of this project are reaching final objectives. Many new studies have developed in the course of this study and will continue. The projects supported by the Energy Research and Development Administration are of utmost importance and consist of: collection of material from uranium miners known to have cancer of the lung into a tumor registry; manual on pulmonary cytology; regression study of sputum cytological findings in uranium miners who showed marked atypical squamous cell metaplasia and have quit smoking cigarettes, mining, or both; continuation of sputum collection and collection of lungs from deceased miners; sensory development for localization of carcinoma in situ of the lung; and lung histology program. Since we have examined approximately 77,000 sputum samples over the last 20 years in cases that showed normal cytology at the inception of the study and some subsequently developed carcinoma of the lung, we have an accumulation of material that is worthy of study and presentation.