This paper discusses the question: what genetic contributions to efficiency of crop plant production may be expected in the next decade or two? Two aspects of efficiency are recognized. General efficiency, reflected in the yield of a standard product, is essentially a matter of conversion of carbon dioxide and radiant energy to a desired product with minimal waste or loss. Minimal waste is achieved by optimal use of the environment and by optimization of plant structure and physiological response. The best opportunities for enhanced yields lie in improved partition of assimilate rather than in enhanced net assimilation. Minimal waste is primarily a matter of disease resistance; field (or horizontal) resistance is likely to become ever more widely used. Control of harvest and storage losses offers little opportunity to the plant breeder. Specific efficiency is reflected in quality and is concerned with altered chemical composition, often, and increasingly, of a fairly well-defined nature. There seems to be a clear trend towards breeding for quality factors. The conclusion is that the 1980s will see further yield advances, together with great improvements in specific efficiency. Thereafter we may well be, in advanced agricultures, approaching plateaux in the yield performance of many crops. If so, the levels of the plateaux will be determined by the degree of success achieved by plant breeding, interacting with such factors of the environment as are accessible to control by good husbandry.