Two theorems derived from Blau's recent macrosociological theory of social structure are tested with data on intergroup criminal victimization in the United States. The data base is taken from the National Crime Survey (ncs) national sample for the years 1973 to 1978. The theoretical predictions tested are that (1) the relative size of the same group in different neighborhood contexts is inversely related to extent ofoutgroup victimization; and (2) neighborhood heterogeneity is positively related to rates of intergroup victimization. These predictions are tested with data on the interpersonal crimes of rape, robbery, assault, and larceny for two major parameters in Blau's theory—race and age. The results support the hypotheses and show that while ingroup victimization is highly prevalent in the United States, interracial and interage criminal encounters are strongly and positively related to neighborhood heterogeneity.