This volume contains papers presented during the science trace at the 3rd International Conference of Business Information Systems, BIS 9, held in Poznan, Poland, 14-16 April 1999, which discussed the development, implementation, applications and improvement of computer systems for business processes. The papers deal with practical, industry experiences and validated prototype implementations, and cover areas such as Decision Support, Workflow Management, Data Warehousing, Business Process Re-engineering. The authors are well-known, and include Klaus R. Dittrich, Johann Eder, Gary Klein, Peter C. Lockemann, Heinrich C. Mayr, August-Wilhelm Scheer and Robert Winter.