This paper presents a novel workflow-based approach to the design and implementation of distributed visualization systems in a Grid computing environment. The approach extends the traditional dataflow visualization system into an environment in which visualization Web services can be linked with local visualization tools to form a pipeline using workflow technologies. A specific aim of our design is to provide a distributed visualization toolkit to fulfill a user?s request for any particular visualization technique/algorithm, allowing a user to select the most appropriate resources and compose the visualization pipeline.