The Spanish and Portuguese Socialists Parties are studied here as part of the research line that conceptualizes the transitions into democracy in Spain and Portugal as the same political and social process. This common democratic "wave" had an important relationship due to its simultaneity, despite the differences between both countries. Improving the knowledge of the transnational dynamics in Iberian social-democracy, one of the main subjects of the democratization process in the Peninsula, is key to comprehend this period.
Keywords: Socialism; Spain; Portugal; Transitions; Democratization.