The new fourth-generation software has enormously eased the burden of computing for users, but they have also created a confusing, difficult problem in software evaluation and selection. Therefore it is argued that a sound and complete evaluation paradigm is a key element in an efficient and effective software system design and use process. While much has been written about software evaluation in general, in the medical field, the guidances and recommendations previously provided are too general to be of practical use. Considering also the other weaknesses of conventional evaluation paradigms we have decided to develop a more adequate one which will have a solid theoretical framework, specific guidances, strict and well-defined taxonomic space, and a fair ranking approach. In the present paper we will therefore introduce our new evaluation paradigm and show its applicability in evaluation and selection of medical software systems according to their usability.