The cyclical behavior of markups is at the center of macroeconomic debate on the origins of business-cycle ‡uctuations and policy e¤ectiveness. In theory, markups may ‡uctuate endogenously with the business cycle due to sluggish price adjustment or to deeper motives a¤ecting the price-elasticity of demand faced by individual producers. In this article we make use of a large …rm-and product-level panel of Portuguese manufacturing …rms in the 2004-2010 period. The biggest empirical challenge is to separate supply (TFP) from demand shocks. Our dataset allows to do so, by containing Financial support by FCT (Fundação para a Ciência e a Tecnologia), Portugal, is gratefully acknowledged. This article is part of the Strategic Project (UID/ECO/00436/2013), under the project Ref. UID/ECO/00124/2013 and by POR Lisboa under the project LISBOA-01-0145-FEDER-007722. Carlos Santos gratefully acknowledges FCT research fellowship CONT-DOUT/114/UECE/436/10692/1/2008 under the programme Ciência 2008. We would like to thank Vasco Matias and André Silva for their research assistance, and INE (Statistics Portugal), especially So…a Pacheco, M. Arminda Costa, and Carlos Coimbra, for their help with microdata. Comments and suggestions by How Dixon, Huiyu Li and by the participants at the 11th World Congress of the Econometric Society (Montréal), 30th Annual Congress of the European Economic Association (Mannheim), 8th Meeting of the Portuguese Economic Journal (Braga) and at at seminars in EIEF (Rome) and ISEG of ULisboa (Lisbon) are gratefully acknowledged. The usual disclaimer applies.