Also published in: A.H. Hansen and R.V. Clemence (Eds), Readings in Business Cycles and National Income, Allen & Unwin, London, 1953, pp. 357-375 ; In previous investigations we have attempted, with the help of statistical methods, to contribute to the explanation of cyclical fluctuations in modern free-enterprise economies, viz., the United States and Holland, 1921-1932. The experience gathered has since been increased by a yet unpublished study of the same type of the British economy in the period 1870-1914. In the present paper we propose to consider critically some of the best-known business-cycle theories in the light of the results of these investigations. We shall not base our observations solely on statistical arguments, however, but also make use, where that seems appropriate, of other considerations. We do not claim to have proved, when constructing our models of the American, English, and Dutch economies, all features laid down in these models to be inevitable. We have presented these models as possible structures, perhaps even as probable structures, which have the advantage that they are at least not contradictory to the statistics used in their construction. Hence, not all our conclusions on some business- cycle theories can actually be proved. Nevertheless we think that our attempts lead to useful suggestions and it is hoped that those who reject our conclusions will at least try to give alternative attempts to explain the real course of the crucial variables in a way similar to ours.