The technique of ion implantation has become a very useful and stable technique in the field of semiconductor device fabrication. This use of ion implantation is being adopted by industry. Another important application is the fundamental study of the physical properties of materials. The First Conference on Ion Implantation in Semiconductors was held at Thousand Oaks, California in 1970. The second conference in this series was held at Garmish-Partenkirchen, Germany, in 1971. At the third conference, which convened at Yorktown Heights, New York in 1973, the emphasis was broadened to include metals and insulators as well as semiconductors. This scope of the conference was still accepted at the fourth conference which was held at Osaka, Japan, in 1974. A huge number of papers had been submitted to this conference. All papers which were presented at the Fourth International Conference on Ion Implantation in Semiconductors and Other Materials are included in this proceedings. The success of this conference was due to technical presentations and discussions of 224 participants from 14 countries as well as to financial support from many companies in Japan. On behalf of the committee, I wish to thank the authors for their excellent papers and the sponsors for their financial support. The International Committee responsible for advising this conference consisted of B.L. Crowder, J.A. Davies, G. Dearna1ey, F.H. Eisen, Ph. G1otin, T. Itoh, A.U. MacRae, J.W. Mayer, S. Namba, I. Ruge, and F.L. Vook.