In spite of prior extensive research on the role of information systems (IS) in controlling interorganizational transactions, very little has been said about the role of handheld computers in inter-organizational control. The literature on handheld computers suggests that their facilities of mobility and connectivity engender usability patterns that are significantly different from those related to static and bulkier computers. Yet, the IS field lacks elaborate models explaining the role of handheld computers in inter-organizational control. This paper draws upon the philosophical assumptions of transactions costs theory to analyze this role. Four scenarios resulting from this analysis are appropriation and institutionalization of technology, and interaction and comprehension between the organizations. It further synthesizes these scenarios to propose four socio-technical systems of control that make electronic data transactions with handheld computers efficient. It argues that handheld computers supplant bureaucratic control, and engender more diverse and resilient systems of inter-organizational control. These roles will require IS researchers to rethink the sufficiency of traditional mechanisms of control suitable for efficient inter-organizational transactions, and induce the next wave of research on the control of electronic data transactions with inter-organizational IS.