The brother of Rafael Grinfeld. His parents was immigrants from Bessarabia. In Rosario he was in touch with the Libre Acuerdo anarchist group and with the Local Workers' Union. In 1926 he was arrested over his propaganda activities and in 1927 he refused to do his military service, fleeing to the Tres Arroyo area and adopting his mother's family name - Jusid - a practice that he kept up for much of his active life: in Tres Arroyos he and other comrades set up the 'Rafael Barrett' Library. He took part in meetings and rallies and toured the country on a num- ber of propaganda tours. He began to become active inside the US (Libertarian Socialist Union) and in the ISL (Libertarian Socialist Youth), bringing these closer to the unions. As the USL and JSL representative he attended an underground con- gress in La Plata in October 1935 which laid thefoundations for the FACA (Argentine Anarcho-Communist Federation). In 1954 the FACA renamed itself the FLA (Argentine Libertarian Federation) and Grunfeld kept up his links withthis organisa- tionand with the labour movement. For aseven year period starting in 1963 he served on the Cultural Commission ofthe FLA's National Council. With the military dicta- torship at its height he helped organise a national congress of the labour movement; it was held in June 1980 and out of it came the trade union association known as the COPENASILI (National Standing Committee for Free Trade Unionism).