Agility is a key characteristic for modern enterprises operating in a highly dynamic environment. The attainment of agility is a difficult issue involving all organizational aspects, such as business processes, information systems, personnel, organizational structure, etc. The ability to respond rapidly to changes by utilizing agile business processes is an important constituent of an agile enterprise. The focus of this paper is business process agility outlining the benefits of event-based business process modeling. To this end, an event-based approach is proposed enabling on-the-fly composition of business processes. The introduced approach adopts the concepts of Complex Event Processing. A conceptual architecture for an information technology infrastructure supporting event-driven business process execution is also proposed.