The article offers a review of modern business cycle theory as developed in the first half of XX¬†century. Marrama analyses the extent of economic literature on these topics, pinpointing the main¬†strands of thought and tools used by business cycle economists. The categorization is set forth according¬†to the different methods adopted. Three of these categories are considered as the most important¬†for understanding the current state of business cycle theory: cyclical aggregative models¬†(using a deductive method only); econometrical aggregative models (deductive and inductive method);¬†empirical researches (inductive method only). The A. shows how the increasing dissatisfaction¬†both with the theoretical models formulated by post-keynesian economists and with empirical research¬†on innumerable particular cycles as provided by the NBER group, was leading to a new¬†synthesis centering on the building up of econometric models.