This thesis deals with classification of the subject field history of medicine. The two classification systems SAB and NLM are compared in order to find out which one is the most adequate to organize a small collection of history of medicine. SAB and NLM are the two most commonly used classification systems in medical libraries in Sweden today. NLM classification system specializes in medicine and SAB is a universal classification system. Our purpose with this study is to find out the pros and cons of each system, whether the systems treat the subject history of medicine in a satisfactory way and what kind of classification system that is better for this assignment, a specific one or a general one. From this we try to draw conclusions about the possibilities of these systems to classify a collection of history of medicine. In this comparative study we have analyzed not only the classification systems, but also the classification codes of 74 documents found at the library of a museum of history of medicine. When choosing a classification system for a collection there are a lot of aspects that need to be considered. These can be grouped into three main categories: theoretical, sociological and economical/administrative aspects. In our analysis we have focused on specific evaluation criteria, of which most are theoretical at nature. The criteria used include layout and index, updates, structure, notation, hospitality and finally specificity and exhaustivity. Although both classification systems showed several advantages our conclusion is that SAB is more appropriate for organizing a small collection of history of medicine. Our main reason for this is the fact that SAB provides the opportunity to show date of the topic discussed within the document, not only date of publication. SAB also allows a document to be represented by more than one classification code, if desired.