This paper presents an exploratory study of Information Systems (IS) competencies of business managers in Europe. Following resource-based theory and a knowledge-based view of IS competencies, an extensive review of the literature is conducted to identify a comprehensive list of IS competencies of business managers. In order to validate the business IS competence model, a Delphi study is conducted using two panels consisting of general managers and IS managers. The results indicate that IS competencies of business managers involve a fluid mix of both explicit and tacit knowledge components, and suggest that ‘core’ IS competencies of business managers involve knowledge and experience in the strategic management of IS. Core business IS competencies involve having knowledge about IS strategy, IS investment management, IS resource allocation, IS sourcing options, IS relationship management and IS change management, and professional experience in IS projects and managing IS. This paper concludes by discussing the implications of these findings and provides several directions for future research.