This investigation of a brain cancer cluster in Missouri used two approaches to 
investigate associations with potential risk factors. In a case-control study in 
a rural town, we interviewed surrogates of cases and controls about potential 
risk factors. We found a statistically significant positive association of brain 
cancer with reported exposure to dental X-rays. Occupation was not associated 
with the cluster in the rural town. In a standardized proportional mortality 
study for the state of Missouri, we calculated the observed and expected 
proportion of brain cancers by occupation and industry in Missouri decedents. We 
found that motor vehicle manufacturers, beauty shop workers, managers and 
administrators, elementary school teachers, and hairdressers and cosmetologists 
had significantly elevated proportions of brain cancer. Brain tumors are 
inconsistently associated with occupation in the literature. Further study of 
brain cancer etiology with respect to dental X-ray exposures seems warranted.