AbstractSome countries face a national dilemma. Spain has rather a dilemma of nationalities. This is chiefly cultural and political with inter-regional disparities tending also to reinforce internal cleavages. Despite its secular conflicts of internal ethnoterritorial accommodation, Spain is an entity clearly identifiable as a country of countries, or a nation of nations. However, the social and cultural cohesion that makes up Spain's unity does not obliterate its internal rivalries. After a long hyper-centralist dictatorship (1939-75), and peaceful transition to democracy (1975-79), Spain has undergone a process of deep decentralisation. The 'open model' of home-rule-all-round has evolved into a gradual process of top-down 'federalization', despite that the Spanish 1978 Constitution does not include the word "federal" in any of its provisions. This paper analyses the main features of the ongoing process of 'devolutionary federalism' and provides with insights concerning the evolution of the competitive interplay among Spanish regions and nationalities.