Workflow technology has reached a reasonable degree of maturity, with a number of both research prototypes and commercial systems available. However, methodological issues have received little attention, and WF developers often have to face the WF development process with neither a methodological support nor a global view of the process. In this paper, we introduce a requirements engineering layer in the workflow development lifecycle. It is organization-based, and follows a bottom-up modeling strategy. In order to capture business processes requirements to obtain a workflow model, we describe the tasks in the process as use cases. The use case model is refined by applying specialization, use and extension relationships, as we go up in the organizational hierarchy. A preliminary workflow model implementing the business processes is obtained automatically from the use case model. The transformation is driven by a set of rules derived from the equivalencies between use case and workflow ...