Workflow technology is established in the business domain for several years. This fact suggests the need for detailed investigations in the qualification of conven-tional workflow technology for the evolving application domain of e-Science. This chapter discusses the requirements on scientific workflows, the state of the art of scientific workflow management systems as well as the ability of conven-tional workflow technology to fulfill requirements of scientists and scientific ap-plications. It becomes clear that the features of conventional workflows can be advantageous for scientists but also that thorough enhancements are needed. We therefore propose a conceptual architecture for scientific workflow management systems based on the business workflow technology as well as extensions of exist-ing workflow concepts in order to improve the ability of established workflow technology to an application in the scientific domain with focus on scientific simulations.