In 1978, Robert Cohen wrote a groundbreaking work applying sociological principles to actor training which went on to influence a generation of theatre and performance studies students and academics. That book was called Acting Power. This carefully revised 21stCentury Editionof an important chapter of theatre scholarship reconsiders its findings in the context of today's field. Cohen's elegant and rigorous updates serve only to emphasise the continuing relevance of his uniquely integrated approach, drawing on an extraordinarily rich career as teacher, scholar, director, translator and dramaturg. This practice found, and continues to find, its most significant expression in Acting Power.