After the Second World War, the United Kingdom has realized a great progress in cereal production. Two factors are related to this progress: one is high prices of cereals and the other is technical advances in cereal production such as the breeding of new varieties of crops, the development of new fertilizers and chemicals, and the improvement of various kinds of farm machinery. High prices of cereals gave farmers much incentive to introduce improved methods of cereal production. An attention should be given to herbicides because they made it easy to adopt continuous cereal cropping by reducing greatly labour input for weeding. Continuous cropping of cereals, however, was suffered from various plant diseases. Pesticides got rid of some, but not all. Another means of disease control was to plant one of the crops other than cereals like oilseed rape on the field after harvesting cereal. Those crops are called break crops. With them, the diseases of cereal crops have been controlled fairly well. The purpose of this study is to trace the changes in cropping systems on cereal farms and to make clear the features of intensification of cereal farming in England. The date analysed are based on the annual “Report of Farming in the Eastern Counties of England” published by the University of Cambridge and the duration observed ranges for 26 years, 1967-92. The study shows that the basic cropping system on cereal farms in the Eastern counties changed twice: first, in the middle of 1970s and secondly, the middle of 1980s. From 1960s to the middle of 1970s, the area planted to cereals, especially to barley, increased rapidly, but the area planted to non-cereal crops decreased. As for barely, the improved varieties of winter barley increased in acreage. A continuous cereal cropping was tried first on barley. Field peas and beans were main break crops at that time. From the end of 1970s to the middle of 1980s, a sharp increase was observed in the area planted to winter wheat and oilseed rape. The continuous cereal cropping was tried on wheat with improved herbicides and pesticides. Incidentally, the prices of oilseeds and beans and peas, protein contained feed for livestock, were supported by the CAP after the embargo on soybeans by the United States in 1973. This price support increased the cultivation of those break crops, especially oilseed rape. Since the middle of 1980s, the acreage of break crops has increased, but that of cereals has decreased. This decrease is due mainly to the measures against the overproduction of cereals and other products. The agricultural stabilizers and set-asides, new instruments of the CAP, are included in the measures. Since agreement in the Uruguay round of GATT negotiations in 1993, the prices of cereals and break crops are expected to be reduced closer to world market levels. The cereal farmers will face in the future a considerable decline in net farm incomes. The ways to meet it will be to enlarge the size of their farms and/or to intensify their farming. Those ways are, however, likely to accelerate ill effects on the environment. Taking the environment into consideration, the reorganisation of cereal farming by making use of break crops with less application of herbicides and pesticides is desirable.