The growing importance of Electronic Data Interchange for the rapid transmission of intra- and interorganizational communications is becoming widely recognized. EDI itself is little more than a faster mail service: it is the opportunity to integrate EDI with internal application systems and organizational functions which separates it from other forms of electronic telecommunications - and makes EDI a truly strategic application, offering comparative advantage at the organizational national and international levels. This paper discusses the results of a series of case studies of Australian organizations involved with EDI, undertaken to determine whether integration with internal application systems can be defined as a series of comparatively standard and recurring stages. The results of the analysis indicate that while such integration does, indeed, occur in a relatively standard manner for a large class of EDI-using organizations, there are also three other classes of organization for each of which a different model is appropriate. Although these additional classes are small in terms of the number of organizations of which they are composed, they are significant in terms of their importance and influence on industry in general and on EDI penetration in particular.