Our paper is about the principles of data collection and usage. The integration of media and product research, the construction of a computer data bank, an explicit model of how media reach people, closer blending of media buying with media planning, the evaluation of advertising performance - we believe that all these are desirable. We outline examples of advances in technique but these are not given in detail and in any case are not beyond improvement. We do not describe just one computer program, but a family of programs with a variety of objectives. They are linked by the data they use and by their systematic approach to the media planning problem.