He studied painting and printmaking at the Círculo Artístico de Montevideo but soon abandoned painting for the print, gravitating toward the woodcut and the lithograph as his primary media. He moved to the United States with a grant from the Guggenheim Foundation in 1945 to study at the Art Students' League and, later, at the New School for Social Research.

By the early 1950s he was already recognized as one of America's foremost woodcut artists and since then has had an influential and revitalizing effect on the art of woodblock printing. By 1968 has was invited to represent Uruguay at the 34th Venice Biennial with a retrospective of his work.

He has supported mass-produced graphic art as a means to expose more people to artwork. His own work has been commissioned for advertising, magazine illustrations, record covers, Christmas cards, and a U.S. postage stamp.

His main focus has been on book illustration into which, like his contemporaries Ben Shahn and Lorenzo Homar, he integrates calligraphic text as part of the design of the print. His beautiful books, many of them for children, have helped introduce North America to the poetry of Lorca, Gabriela Mistral and Neruda and foment interest in the works of Whitman, Thoreau, Dylan Thomas and Poe.