: Grid computing infrastructures and service-oriented architectures commonly rely on web services as their implementation technology. This technology allows complex workflows to be designed and executed by workflow engines in either Grid or standard web service environments. Nevertheless, the integration of human intervention in Grid workflows is still a manual, therefore time-consuming and error-prone task, caused by the lack of software support for designing workflows that incorporate human tasks in Grid environments. In this paper, we present a model-driven approach for designing Grid workflows containing human tasks. The solution also covers the automatic creation of user interfaces for human interventions. The approach is implemented and validated by a virtual prototyping process from metal casting.