The stylistic elements employed by Hans Arp (1886–1966) revolutionized the way people thought about the medium of sculpture. His sculptural work does not allude to role models or fantasies, but instead allows imaginary images to appear in an open process. Arp’s importance to art history has been overshadowed in recent years by discussions about originals and imitations that arose in conjunction with the founding of the Arp Museum Bahnhof Rolandseck. Two independent scholars, Arie Hartog and Kai Fischer of the Gerhard-Marcks-Haus in Bremen, have assembled the available data on Arp’s body of sculptural work, an important step toward clearing up the debate. This publication assembles all of the authenticated examples of every one of his known sculptures and brings their respective status up to date. An introductory essay describes the posthumous development of Hans Arp’s oeuvre.