Ontologies are becoming increasingly common in the World Wide Web as the building block for a future Semantic Web. In this Web, ontologies will be responsible for making the semantics of pages and applications explicit, thus allowing electronic agents to process and integrate resources automatically. The ability to integrate different ontologies meaningfully is thus critical to assure coordinated action in multi agent systems. In this paper, we propose a strategy and tool, CATO, that allow for totally automatic ontology alignment for the Semantic Web.