Abstract: This thesis concerns the Design and Evaluation of a Web Based Environment for Teaching and Learning.The research aim is to give contribution to four conceptual critical issues in Web Based Training.The first issue treated is the development of an instructional design mode for the World Wide Web to promote instructional strategies fostering an effective use of this environment in education.The second issue is the design and realization of an interactive course environment, based on the instructional design model previously defined, in terms of services and functionalities available for an effective use of the Web as a cognitive learning environment. This approach is implemented and evaluated for the teaching of technical disciplines.The third issue is the model for the development of professionals and faculty which are going to work in the educational technology field, addressing the problems of changing of roles and duties.The last issue is the development of a model for the hypermedia representation of a course content, which emphasizes the necessity to support authors in the conception of the concepts representation on the Web.