This study aims to consolidate the economic history of Quebec over the period from 1948 to 1980. Unlike previous economic studies relating to this period, we identify the chronology of the economic cycle of Quebec by estimating the real quarterly GDP by using the method of Ginsburgh (1973) as modified by De Carufel and Lizotte (1982). Our analysis of the duration and intensity of recessions confirms the presence of regional cycles in Canada. Il shows also that the business cycle of Quebec is more strongly correlated with the US cycle than with the cycle in the rest of Canada.