This paper presents an approach that aims to integrate intelligent agents, user models and automatic content categorization in a virtual environment. In this environment, called AdapTIVE (Adaptive Three-dimensional Intelligent and Virtual Environment), an intelligent virtual agent assists users during navigation and retrieval of relevant information. The users interests and preferences, represented in a user model, are used in the adaptation of environment structure. An automatic content categorization process, that applies machine-learning techniques, is used in the spatial organization of the contents in the environment. This is a promising approach for new and advanced forms of education, entertainment and e-commerce. In order to validate our approach, a case study of a distance-learning environment, used to make educational content available, is presented.