Customer behavior is determined by several factors. Since the products/services are delivered to the customers, their usage of the products directly affect those products. The research data offer guidelines on how to manage customers’ behavior. Quantitative research trains manufacturers to govern customers’ behavior, while qualitative research requests a certain type of information for the purpose of the research. Each company has to know how to maintain a client and how to gain a new one. Customer Relationship Management enables orientation towards the client by different methods and marketing strategies with the purpose of developing a long-term relationship with the client. Extra values should be administered towards every client in order to create satisfaction. Clients become more loyal and the chance of remaining consistent with their company increases. Loyalty is a situation in which a client buys again a certain product. Information technology significantly helps companies achieve profitability on the market and maintain their clients. The main task of information technology is too add values to its clients, activities, and processes. First, the market requirements need to be analyzed so that this data could be stored in the databases necessary for every company’s business. CRM is a strategy that enables collecting, storing and processing the data. It gives information on clients and their consumption and benefits. There is a method that reveals new information from the data, which is called data mining. Data mining helps separate the important data from the unimportant so that the patterns between them could be determined. PHOENIX Farmacija d.d. makes decisions based on the analysis of their clients and maintains the clients and creates loyalty by the application of the data mining method. This paper shows the process of data collecting, the process of storing in databases and the process of data mining which provides the required information.