John Porter's landmark study of social and ethnic inequality, The Vertical Mosaic, became an instant classic when it was first published in 1965. A national best seller that sold more than 100,000 copies, the book was the first major study of Canada's class structure and one of the foundational texts in Canadian sociology. Sociologist Irving Louis Horowitz described it as "the sociological study of present-day Canada." Fifty years later, the book retains vast significance both for its powerful critique of social exclusivity in a country that prides itself on equality and diversity and for its influence on generations of sociological researchers. The 50th Anniversary Edition features new material which contextualizes the legacy of this important book: a foreword by Porter's colleague, Wallace Clement, and his biographer, Rick Helmes-Hayes, and a new introductory essay by historian Jack Jedwab and sociologist Vic Satzewich.