In seven different groups of prison inmates, violent criminals had substantially higher levels of lead or manganese in their hair than nonviolent criminals or law-abiding controls. Otherwise puzzling geographical differences in rates of violent crime in the U.S. are highly correlated with environmental pollution and death rates from alcoholism. Counties in which the EPA did not report industrial releases of either lead or manganese, and where alcoholism was lower than average, had a rate of 228 violent crimes per 100,000 people (well under the national average). In contrast, counties with industrial releases of lead and manganese and higher than average alcoholism had rates of violent crime of 969 per 100,000 (three times above the national average). (The statistics linking differences in the rate of violent crime to lead, to manganese, and to alcoholism would each occur by chance less than once per 10,000 times.) Controlling for 17 other factors, including population density, poverty, and ethnic composition, the three sources of neurotoxicity are significantly associated with violent crime.