This paper reviews the problem of radiation-induced carcinoma of the lung in the fluorspar mines of Newfoundland. Seventy-eight workers have died from this disease since commercial operation commenced in 1933. In 1959 the source of the radiation was identified as radon, and its daughter nucleotides present as contaminants in water seeping into the mines. Heavy smoking is probably a synergistic cocarcinogen. The histology in this group of patients with radiation-induced lung cancers is unusual, since squamous cell carcinoma accounts for 90 percent of all cases. There have been four patients with second primary lung cancers. Radical radiotherapy has been the primary mode of treatment based on the reluctance of the miners to undergo operation. Surprisingly good results have been obtained, with an average survival time of 34 months after treatment. Institution of improved ventilation has reduced radiation to safe levels, but an estimated 120 miners from the pre-1960 era are still at risk.