The paper treats the problem of building successful brands from the perspective of a simple yet comprehensive theory of consumer markets. It is practical, using case study material from projects for Premier Biscuits and other clients, to demonstrate how the theory and its associated techniques add objectivity and direction to strategic and tactical market planning. The model and systems which are described were originally developed by Marcos Ltd. and are marketed by Taylor Nelson under the brand name Optima. Premier Biscuits are well known for their biscuit products which are sold internationally under the Cadbury's brand name. To adopt a truly holistic approach to developing and managing successful brands demands a viable understanding of how markets work. This means that it is necessary to get below the observed behaviour of the purchasers to the underlying physics, if we may use the word, of the dynamic systems which we call markets. The Marcos consumer choice model, based essentially on the assumption that purchasers choose the brands which suit them best at the time, fits real markets accurately and consistently. It tells us why those brands which have a clearly defined meaning and a relevant relationship with the consumer are best positioned for success and what other elements are necessary. A brief practical account of the model is given, followed by an illustration of how it is Possible to model consumer panel data using it. The example is used to throw important light on the relative roles of brand positioning and brand enhancement in advertising and to discuss how markets evolve. The application of the model to the problem of managing a brand portfolio is described. An example is given of the way in which the model can be used to identify the gaps in a manufacturers brand portfolio and to describe in detail the brands which would fill them. This illustrates some of the many uses of the techniques and model in ad hoc consumer studies. A technique for predicting the sales of new products by analogy with existing products using ranking methods is described. This leads into a discussion of the processes involved in the establishment of a new brand within a market, focusing in particular on the roles played by advertising and the use of sampling to force trial. Finally spotlight analysis is used to identify the meaningful options available for advertising a particular brand. This leads into further discussion of brand positioning and brand enhancement.