No / Dominance effects are normally associated with multinational corporations (MNCs). However, we argue that a strong local competitor can create ‘dominance effects’ setting the institutional parameters for employment relations in multinational subsidiaries. Moreover such an effect can be persistent. In this case the Spanish-owned El Corte Inglés (ECI) used its power and influence to establish an employer's federation and two ‘yellow unions’. These yellow unions infiltrated the French-owned MNC Carrefour and most of the Spanish supermarket sector by the early 1980s and continue to dominate collective bargaining rounds and works council elections, marginalizing the main independent trade unions. This has resulted in poor pay and working conditions and a lack of effective employee representation across most of the Spanish supermarket sector. The fact that Carrefour established an international framework agreement to observe union rights in 2001 has as yet not changed this situation.