As corporations continue to introduce workflow systems, different systems have appeared for processing of core-business tasks for information processing and clerical work. A number of different models for coordination of different workflow systems have been proposed; but workflows for core-business tasks constitute the central business processes of the company, and certain aspects of coordination of such workflows differ from other kinds of coordination. This paper clarifies these differences, and proposes a model for coordination, which takes these differences into consideration. In addition the application of this model to an actual system and confirmation of its effectiveness are also reported.