Diversity has powerful advantages, but may also generate internal tensions and low interpersonal trust. Despite extensive attention to these questions, the relationship between diversity and trust is often misunderstood and findings methodologically flawed. In this article, we specify two different mechanisms and adherent hypotheses. An individual might base her decision to trust on her perceived social similarity in relation to others in the community, that is, a similarity hypothesis. However, in a homogenous context, she might expect trustworthy behavior irrespective of her own social position due to signals of low degrees of social conflict and dense social networks, that is, a homogeneity hypothesis. Prior research has pinpointed only one of these mechanisms. The homogeneity hypothesis has not been explicated, and when the intention has been to test the similarity hypothesis, the homogeneity hypothesis has unintentionally been tested instead. The results are straightforward. While the homogeneity hypothesis is strongly supported, the findings speak against the similarity hypothesis.