Affective relationship commitment has in several studies been identified as a crucial factor in the longevity of business relationships. In this article, it is argued that affective commitment should be researched on the individual level rather than the organizational level and that relevant psychological processes need to be incorporated into theory in order to increase understanding regarding the dynamics of this aspect of relationship commitment. The psychological contract, a construct derived from organizational psychology, is tested as an antecedent to affective commitment in relationships between buyers and sellers in the market for industrial supplies in Sweden. The findings indicate that the relational orientation of the psychological contract, as well as the evaluation of the same, has explanatory value when related to affective commitment in business-to-business relationships.