The article is an attempt to test empirically the inequality theorem, a major theorem in Peter M. Blau's theory of intergroup relations. The theorem states that social inequality is conducive to social integration in the sense that an increase in inequality creates associations between members of different strata, even fairly distant ones, more probable. Social integration is understood broadly here in terms of rates of intergroup relations. A specific definition of the concept was proposed in the framework of the models of relational inequality which are discussed in detail in the article. These models allow for precise definition of the level of social inequality and the extent to which a society is integrated. In the empirical test of the inequality theorem, data from 7 editions of the Polish General Social Survey were used. To assess fit of the model tested, linear regression through the origin was employed. High values of the coefficient of determination obtained by the model indicate its good fit which, in turn, suggests that the inequality theorem is an appropriate description of the relationship between inequality and integration, even though it is highly counterintuitive.