In business environment data warehousing - the practice of creating huge, central stores of customer data that can be used throughout the enterprise - is becoming more and more common practice and, as a consequence, the importance of data mining is growing stronger. Data mining allows indeed to extract the most important information from such vast data and to uncover previously unknown patterns that may be relevant to current business problems, thereby helping business managers to transform data into business decisions. In marketing data mining has several and profitable applications. It can help to identify market segments containing customers with high-profit potential, and then build campaigns that favorably impact their behavior; to detect customers dissatisfied and ready to leave, and then align campaigns more closely with their needs; to outline profiles of prospective customers, and then increase the response rates of the acquisition campaigns, and so on.