The development of market research and marketing shows us that, based on a series of market research results, the patient is playing an ever larger role in the marketing strategies of the pharmaceutical industry. We can see that the patient receives his information via the communication channels physician, pharmacist and mass media. In order to check the efficiency or penetration of these measures, the patient monitor has been developed by Marplan, which is based on data from 12-15000 patients per year, gained from representative questioning of the population, at regular intervals. The potential uses of this instrument are shown, based on a pretest, which had already been carried out. Of utmost importance is the question, whether with similar products, potential target groups can be reached in different ways, and how to find out the causes. It would be the job of marketing to discover whether changing the product or the marketing strategy would raise the market share for specific target groups.