Ontologies are emerging as a key solution for knowledge sharing in co-operative business environment. From the technology point of view, the growth of Internet use has favoured the development of environments devoted to collaborative and distributed work, allowing different communities to increase flexibility and effectiveness in their work. From the representation point of view, an ontology management system represents a powerful tool to create common and shareable knowledge repositories. The goal of this work is to present SymOntoX, a web-based ontology management system. It is an open source environment supporting collaborative and distributed ontology construction and maintenance.