The Department of Mathematics at the University of Food Technology, Plovdiv, Bulgaria, has introduced the Computer Algebra System DERIVE into the Mathematics courses with a view to increasing student motivation and understanding of the material taught as well as the efficiency of the teaching process. With the aim of investigating the effect of using CAS on the teaching and learning process regular observations of the class work have been made and special evaluation forms to measure class progress were completed by the teacher after each class. This report describes the organisation of CAS-based classes as well as the reflective approach taken in designing the materials and the CAS-based classes' structure. (Contains 1 table.)