In this paper we discuss the structure of training cases in web-based and case-oriented training systems. We obtain these results from the development of a training system in medicine, " Docs 'n Drugs – The Virtual Polyclinic". First, we discuss a solution according to the medical application domain. The main idea there is to represent training cases in three separate layers of knowledge. Then, we generalize these results and show that the concepts also apply to other subjects areas where case-oriented learning occur. We draw conclusions and mention benefits of this approach.