Brazilian labour unions have an excellent reputation in international trade union circles, often being depicted as one of the most dynamic and militant labour movements today. In Brazil, however, many scholars criticize the unions for having abandoned the struggle taken up in the late 1970s against the industrial relations system and the limits it imposes on their actions. Since its creation in the 1930s, the authoritarian corporatist labour relations system has, in fact, proven to be extremely resilient. It survived two periods of intense political upheaval-the trade union movement having played a predominant role in both-and radical change to the country's economic model without undergoing major transformations. The adoption of a new Constitution in 1988 introduced only minor alterations, leaving the pillars of the corporatist system intact until today.In this article, we put to the test a widespread, determinist vision of Brazilian trade unionism, according to which unions maintain a paradoxical yet atavistic relationship with the heavy body of laws that provides them with advantages while limiting their freedom. In order to reflect on this, we performed field enquiries on two trade unions carefully chosen for their archetypical profile. Our research activities were conducted in the midst of the debate (from June 2005 to July 2006) on the ambitious project to reform the industrial relations system, initiated by former trade union leader and Karen Lang is an independent researcher in Sao Paulo, Brazil (ruthylang@hotmail.com).