Begins by critically reviewing Vicker's list of reasons why business competition is likely to lead to productive efficiency, and then argues that traditional economic concepts of competition and productive efficiency need to be broadened to take account of dynamics and uncertainty, and of the importance of economic interdependence which is not based on competition. The structuralist approach to competition policy is examined and particular attention is given to the 'structure - conduct- performance' paradigm. It is suggested that competition policy in practice tends to emphasize structure rather than conduct and is highly static in orientation. Although earlier, most members of the Chicago School e.g. Stigler, supported a structuralist approach to competition policy, more recently several Chicago economists have proposed the "efficiency defense" of market concentration, namely that dominance in an industry is almost always a result of superior efficiency. This evolutionary Darwinian-type defence is based on dynamics and converges towards the Schumpeterian view. Hayek, like Schumpeter, had an interest in competitive processes but the competitive models of these two Austrian-trained economists are very different. The model of Schumpeter is open whereas the system of Hayek is relatively closed and unable to take account of the competitive complexities of modem economic systems. Despite Hayek's interest in processes, his recommended competition policy is structuralist in character and similar to Stigler's.