"CAS, Educational Microworlds, and the Internet" Nurit Zehavi Weizmann Institute of Science, Israel Email: ntzehavi@weizmann.weizmann.ac.il Constructing learning environments that incorporate CAS, elements of educational microworlds, and the Internet can boost the implementation and utilization of these technologies in mathematics education. The desire to provide educational materials over the Internet has led us to consider integrating our experience in developing open tutoring systems and in creating non-routine problems to be solved using a CAS. An open tutoring system should enable students to find solutions in their own ways, and an on-line guidance, in the form of hints, should provide support. Investigating non-routine questions using CAS encourages diverse mathematical thinking and independent work. With this in mind we have analyzed the types of mathematical knowledge that were applied in solving specific problems and identified the relationships and the 'Webs of meanings' involved in the solution processes. We utilized computer software tools commonly used in the Internet, such as html, CGI, Java Script, and e-mail to design an interactive guidance system in the format of Web pages. The pilot studies in this new development dealt with Magic circles obtained by composing linear functions, and with a specific sequence of Extrema problems. The progress so far indicates that the work to be done is indeed a triple challenge.