Ontologies are becoming increasingly important in a variety of different fields, such as intelligent searching on the web, knowledge sharing and reuse, knowledge management, etc. Therefore, we expect that the need for tools to support the construction of ontologies will increase significantly in the coming years. In this paper, we investigate several of these tools. We evaluate the tools using two different ontologies: a simple one about university employees, and a second, more complex one, about the structure of a university study. The evaluation was conducted using a framework, which incorporates aspects of ontology buildings and testing, as well as cooperation with other users. Our conclusions are that the usefulness of the tools depends on the level of the users and the stage of development of the ontology.