A better understanding of how interorganizational information systems (IOIS) are adopted is important since a successful implementation of information systems (IS) can be expected to raise long-term organizational efficiency. However, organizations often find IOIS adoption to be a bumpy ride, and despite the apparent reason to come to terms with IOIS, the utilization rate is still low. IOIS adoption is an interesting process to study, because of the high complexity in successful adoption of IOIS created by the increased number of organizations involved in the adoption process. This literature review found four different streams of research: 1) studies explaining why organizations adopt or reject IOIS by investigating factors determining adoption of or barriers to IOIS adoption; 2) studies explaining how to create the desired organizational effects from IOIS; 3) studies explaining how IOIS are affecting the buyer-supplier relationship they are introduced into; and 4) studies categorizing the structure of IOIS adopters in different configurations. Seemingly only limited effort has been made to study the actual adoption process. This apparent lack of studies of the adoption process calls for research opening the black box of IOIS adoption.