This article casts new evidence on the e¤ects of decentralization on economic growth. Based on the literature on the e¤ects of institutions on the economy, such e¤ects are assumed to accrue through total factor productivity (TFP ). We try to overcome the recent criticisms of the empirical approaches regarding the proper measures of variables capturing decentralization. Thus, …ve variables to capture decentralization are proposed. Panel data for the regions of Spain over the 1986-2010 period are used. The results show that the …nancial autonomy and the share of regional investment in public infrastructure seem to positively a¤ect the economic growth of Spanish regions. However, a negative e¤ect is found for the number of responsibilities transferred to the regions. Moreover, the empirical evidence could be suggesting that the Spanish state might be near or surrounding the optimal level of decentralization. Results are fairly robust to di¤erent estimation methods and measures of TFP, regardless of the assumption of constant returns to scale.