Portuguese trade unionism had a history of militancy and radicalism. Its roots go back to the late nineteenth century when modern industry first appeared. The unions grew during the period of the First Republic, 1910-26, when they enjoyed freedom to organize. It was in this period that Marxist, Bolshevik, Trotskyite, anarchist, and syndicalist ideas were discussed and disseminated. Although the labor movement was small, a reflection of the low level of Portuguese industrialization, it was active and vocal.

During the Salazar-Caetano era, militant unions were abolished, and the labor movement was forcibly subordinated to corporatist controls. Many labor leaders were jailed or sent into exile. Some cooperated with the new corporative system others organized a militant, communist-controlled underground labor organization. With time this union, Intersindical, was well enough established that the government actually dealt with it almost as if it were a legal bargaining agent.

During the Revolution of 1974, Intersindical, or as it came to be known in 1977, the General Confederation of Portuguese Workers-National Intersindical (Confederação Geral dos Trabalhadores Portugueses-Intersindical Nacional--CGTP-IN), was at last able to function as a legal labor organization, and it expanded rapidly. Controlled by the communists, CGTP-IN was closely associated with the PCP's bid for power and for a time was the only union permitted to function. Soon, however, it faced opposition from the socialist labor organization, the General Union of Workers (União Geral dos Trabalhadores--UGT). For a time, the communist labor group was overwhelmingly dominant, but during the 1980s the UGT grew in size, especially in the service sector, and by the end of the decade its overall membership was about half that of CGTP-IN. Many other small unions were active at the beginning of the 1990s, most notably those representing highly specialized professions such as airline pilots. There was also a Christian democratic trade union movement.

After 1974 organized labor emerged as a powerful force in Portuguese politics, although its influence waned somewhat after the revolutionary period. Union membership was not high, and as of the early 1990s only about 30 percent of the work force was unionized. The communist-led unions were not able to block the constitutional amendments of 1982 and 1989, which reduced the radical legacy of the revolution. Moreover, some unions backed away from the intense ideological unionism of the 1970s in favor of more limited and practical objectives.

Data as of January 1993