Two main findings support the utility of using social disorganization theory to explain county-level American Indian homicide rates: both family disruption and ethnic heterogeneity had significant and positive effects on American Indian homicide rates. Two other findings, however, did not support a social disorganization explanation for county-level American Indian homicide rates: neither American Indian poverty nor residential mobility were significantly related to homicide rates. The authors conclude, however, that social disorganization significantly affects American Indian homicide rates. The findings have implications for public policies that address the high rates of homicide among American Indians because they suggest the need to stabilize disorganized communities. Data on homicides were gathered from the Federal Bureau of Investigation’s Supplemental Homicide Reports for the years 1986 to 1992 in all U.S. counties having an American Indian population of at least 1 percent. County-level data on age, race, crime, and housing were gathered from the Microcase Data Archive of States, Cities, and Counties for the years 1980 through 1990. Main variables under analysis included poverty, population mobility, ethnic heterogeneity, and family disruption. Control variables were percentage of population aged 15 to 29 years and size of county population. Statistical analyses included the use of negative binomial regression models. Future research should further investigate the social disorganization concept of mobility because it may be that movement within the same State may not be influential enough to affect county-level social disorganization. Tables, notes, references