As part of an investigation into the high mortality from lung cancer and the high sex ratios of births in Armadale, central Scotland, concentrations of arsenic were measured in soil cores from 48 sites in Armadale and 6 sites in a comparison town. Concentrations in Armadale were substantially higher than those in the comparison town, and many of the highest range of values were in that part of the town where the epidemiological abnormalities of lung cancer and of birth sex ratios were most pronounced. The study indicated that clues to the etiology of high rates of disease in small areas could be sought most profitably if close links were maintained between epidemiological and environmental investigations.