The present work is aimed at filling a hiatus in the literature dealing with the Young Hegelians and the early thought of Karl Marx. Despite the prevalent view in the past few decades that Bruno Bauer played an important part in the radical activity of Hegel's young disciples in the eighteen forties in Germany, no comprehensive work has so far been published on the relations between Bauer and Marx. In 1927 Ernst Bar­ nikol promised to write a monograph on the subject, but he never did. For the purpose of this study I perused material in numerous library collections and I would like to express my gratitude to the staff of the following institutions: Tel Aviv University Library, the Library and Archive of the International Institute of Social History in Am­ sterdam, the Heidelberg University Library, the Library of Gottingen University, the Tiibingen University Library, Frankfurt University Library, the State Library at Marburg, the Manuscript Department of the State Archives in Berlin.