This paper looks at the problems of managing large retailing organisations and the implications for the design of an effective marketing information system. Six broad problems are distinguished - increasing concentration in retailing, increasing power over suppliers, fewer buying points, the proliferation of new products, profits highly sensitive to price and volume changes and great differences between shops. These define the information needs of the decision-maker. The objective is to design a system which can appropriately meet these needs. A case study is developed which shows how a comprehensive system can be applied to meeting the organisational buyer's decision needs. The model is based on a screening technique with parameters developed from past data on costs and product performance.