MICROECONOMICS, THEORY & APPLICATIONS is an e-learning CD-ROM produced by BWM MEDIASOFT and Professor of Economics Bertrand Lemennicier from the University of Paris Panthéon-Assas. It is a new way to learn economics. A good competence in microeconomics means controlling the art and the way of practising the economic reasoning. To publish one's course on the Internet and on a CD-ROM has some advantages compared to a normal edition on paper. The course is brought up to date in real time, the errors can be corrected immediately, the more important graphs are animated, there are links towards the most important economic works, the student can at any moment ask a question to his professor and finally the problem sets are interactive. The student has to answer the questions as if he was in exam and he has the possibility of knowing the grade that he would have for his answer. He can also ask questions and discuss with the professor to better understand the solution to the questions. This way of learning improves drastically the success to final exams. For teachers the CD-ROM offers a great number of problems with solutions, discussions and applications which help them to develop their courses. For anybody who wants to learn intermediate level of microeconomics without spending a lot of money by taking formal lectures at the university, the CDROM is a cheap and good alternativeSuch a new way of publishing a textbook is not the outcome of a will to innovate. This course is edited in the form of a CD-ROM and not in the traditional form of a book for three reasons. The first reason - is linked to the pressures and censures that were exerted by my French colleagues to prevent the publication of this textbook at the Belgian editor De Boeck. I make a point here of thanking them because without them I will undoubtedly not have published this textbook on the Internet nor thought of finalising this investment of several years of work by the product that you have in front of your eyes. The second reason -results from a discovery process. To publish one's course on the Internet then on a CD-ROM has some advantages compared to a normal edition on paper. The course is brought up to date in time real, the errors can be corrected immediately, the more important graphs are animated, there are links towards the most important economic works, the student can at any moment ask a question to his professor and finally the problem sets are interactive. The student has to answer the questions as if he was in exam and he has the possibility of knowing the grade that he would have for his answer. This will allow him to memorise the answers and improve his grade at the final exam. The experience shows that the students read the answers without necessarily understanding them or remembering what they read. For a long time the professors ask at the exams the same questions as the students had to answer during the practical work. This is because they are frightened of giving low grades at the exams. But in spite of that many students are not able to answer these questions. The course and the problem sets in the form of a CD-ROM become a very useful teaching aid that replaces very well the lectures and the practical work in small groups. Each student, at any moment, has the possibility of contacting his teacher via e-mail, to ask him explanations on a given exercise, problem, essay or part of the course that he does not understand. This is impossible in a lecture hall or even in the small room for practical works. The student could save time not going to the lecture or to the practical work without necessarily sacrificing his grades and the university avoids investing in huge lecture halls which stay empty two weeks after the school begins. Finally, the teacher has a personal and at the same time anonymous contact with his students who can write him under pseudonyms. The third and last reason - is more prosaic. It makes it possible to an author to do it without a traditional publisher: - who often requires to be subsidise to publish you, because his costs are high, - who most of the time makes no publicity to sell your textbook, - who, in addition, checks if you have a public before accepting to launch himself in this adventure so much he is frightened of losing money, - who asks the public libraries to buy the book to allow him reaching very quickly the dead point, - finally, who pays insignificant royalties to the author for his intellectual production.