Most industrial companies have only a few customers and suppliers that account for a major part of their total sales and purchases. These and relationships to third parties are decisive for the performance of the company, whatever various measures of performance one might use. Sales volumes, profitability, growth potential often depend on only a limited number of relationships. A study of more than 100 Swedish companies shows that the ten largest customers and the ten largest suppliers account for more than two-thirds of the total sales and purchases in two out of every three companies (Håkansson 1989). Data available from PIMS data base (e.g. Cowley 1988) and other large-scale studies on hundreds of companies in Europe (e.g. Perrone 1989) produce the same findings. We thus have indications that situations such as the one described in Figure 1.1 are by no means an exception; they are frequent and perhaps the most typical case.