This population-based case-control study of North Carolina workplaces evaluated the hypothesis that employers' policies allowing firearms in the workplace may increase workers' risk of homicide. Workplaces where guns were permitted were about 5 times as likely to experience a homicide as those where all weapons were prohibited (adjusted odds ratio=4.81; 95% confidence interval=1.70, 13.65). The association remained after adjustment for other risk factors. The findings suggest that policies allowing guns in the workplace might increase workers' risk of homicide.