Extending Small and McDermott’s ‘conditional perspective’, Blalock’s minority competition theory is used to explain how the relationship between African Americans and the number of supermarkets in a zip code depends on the city in which it resides. The 2010 American Community Survey and ZIP Business pattern data are examined with hierarchical general linear models to explore whether the previously observed negative relationship between the percentage of African Americans and the number of supermarkets in a zip code depends on the percentage of African Americans in the city. The results show that the relationship between the percentage of African Americans and the number of supermarkets depends on the percentage of African Americans in the city in the U-shaped pattern predicted by minority competition theory. Applications of minority competition to other theories of the unequal distribution of resources in cities are discussed.