Since the 1940s Gianni Mattioli's collection of modern art has been a touchstone of the history of twentieth-century collecting, both for the quality of its masterpieces and for its underlying program. Mattioli was guided by the double purpose of representing and re-establishing the major movements of modern Italian art and of presenting them coherently to the public.This major new contribution to our knowledge of Italian modern art is the catalogue of twenty-six works in Mattioli's collection, dating from 1910 to 1921, which in 1997 were placed at the Peggy Guggenheim Collection, Venice. Each painting is studied in an essay that explores its origins and iconography, its relation to Italian and international pictorial sources, its position in contemporary aesthetic debate, and its critical history.