The rapid growth of global telecommunication networks, and in particular the Internet, has placed emphasis on electronic mail's potential as an interorganizational communication medium allowing people from different organizations to communicate, gather information, form teams, and pass knowledge across time and place. An important area of research is to understand those factors affecting interorganizational computer-mediated communication usage decisions. This study examines how interorganizational electronic mail (email) systems are being used and what factors relate to this use. This was accomplished by electronically surveying a randomly selected sample of interorganizational email users. The 613 Internet-based respondents were located in 20 different countries and were from education, business, and government. This research examines the characteristics of interorganizational email users, their perceptions of task and channel attributes, and the relationship between these characteristics and interorganizational email use. Three empirically derived patterns of interorganizational email use emerged that showed it was regularly used for broadcast, task, and social communication. Broadcast usage, which reflects an information- gathering communication function, most likely through public bulletin boards, electronic discussion groups, and list servers, was the most frequent use of interorganizational email. Multivariate regression tests showed that the three different usage types were best predicted from different sets of independent variables. Results support past claims that there is a need to differentiate among types of use in explaining computer- mediated communication usage behavior. Implications and recommendations for both researchers and practitioners are drawn from the results.