This thesis deals with the topic of category management in online retailing. Its goal is to identify the assortment factors that affect a company's financial performance. The result of the thesis work is a model applicable in strategic decision making on assortment. The first part consists of basic concepts of retail, marketing and strategic management. The purpose of this part is to provide the reader with the theoretical background for the following practical part. The research for the practical part is conducted on the basis of interviews with experts in the field and the author's own research in business. Each chapter presents a group of metrics that are based on analysis of business data in online retail market. Metrics describe the sp...