Since the Topic Map standard describes a prospective knowledge-structuring model that can be used in a huge variety of knowledge domains the amount of applications utilizing this standard grew enormously. Anyhow, as far as we know, there is no distributed editor of Topic Maps available on the market, that supports an intuitive possibility to manipulate or visualize Topic Maps in the World Wide Web environment. Therefore, TMNet intends to close this gap. As a result, a high performing distributed editor is achieved, with which web-based e-learning environments as well as knowledge environments can be enhanced by supporting semantic data descriptions of their knowledge structure. Additionally TMNet enables the user to extend the structures in an easy way and gives the web developer an opportunity to integrate it into websites easily.