The paper traces the genesis and development of the Kilusang Mayo Uno (KMU) or May First movement in the Philippines as a significant component of Filipino industrial relations. The argument of the paper is that the growth has been rapid despite employer victimization and violent state repression, because of the attractiveness of a new trade union organizing style, a style which has emerged in certain Third World and other repressive state contexts. While the KMU leadership has adopted the political identity, ‘National Democratic Unionism’, I argue that the analytical concept social movement unionism is an effective way of capturing the dynamic of this new trade union form. Through the rootedness of social movementism in the workplace and in the community, through the movement's mass actions challenging state power, and through the leadership conviction that an alternative society is possible, the new form has proven viable. The optimism underlying these developments stands in sharp contrast to the decline of trade unionism in the advanced capitalist societies.