e-Business transformation has become a critical imperative for most organizations today. However these transformations require specific skills, capital, information, technology, access to markets, and core resources that many traditional firms lack. To obtain these resources and capabilities, firms are increasingly turning to external arrangements, such as alliances. Our understanding of why firms choose a particular e-business alliance form over others in such a relationship is limited. Drawing upon social exchange and institutional theories, we examine how partner relatedness and institutional factors drive the choice of e-business alliance form. Results from 1,381 e-Business alliances provide a strong first reflection of the impacts of factors on the choice of e-Business alliance form.