Until recently, one-to-one marketing, the ability to sell targeted goods to an individual based on their known or perceived needs, was not possible for most product types on a mass basis.. Indeed, marketing practice in recent years centered around segmented marketing, in which people are treated as members of groups with similar interests and marketing is done at the group level. However, recent advances in information technology, including the Internet and its World Wide Web, database management systems, computer graphics, and electronic mail, as well as increased processor speeds, now permit one-to-one marketing on a mass basis over the Web. This tutorial explains the concept of one-to-one marketing, including how companies can aspire to move in this direction. It outlines a set of one-to-one marketing practices on the Web and explain how advances in information technology made these practices possible.