Traditionally, in trying to understand the determinants of the prescribing decision, pharmaceutical market researchers have focused almost exclusively on the attributes of their drugs as the drivers of the product choice. But we know that physicians treat different patients differently. What is it about one patient that leads a doctor to prescribe Drug A while another patient receives Drug D? By understanding the role that patient factors play in the prescribing decision, pharmaceutical marketers will be better able to understand the behavior of their customers and in turn be better able to market their products to their customers needs. In addition the paper shows how this new approach can also help to position a product; and how commonly available data can be mined to develop a deeper understanding of how a product is being used, that is, for which types of patients or segments of patients is the drug being used.