This volume represents the Proceedings of the Oji International Seminar on the Application of High Magnetic Fields in the Physics of Semiconductors and Magnetic Materials, which was held at the Hakone Kanko Hotel, Hakone, Japan, from 10 to 13 September 1980. The Seminar was organized as a related meeting to the 15th International Conference on the Physics of Semiconductors which was held in Kyoto between 1 and 5 September 1980. From 12 countries, 77 de legates participated in the Seminar. This Seminar was originally planned to be a formal series of International Conferences on the Application of High Magnetic Fields in the Physics of Semiconductors, which was first started by Professor G. Landwehr in 1972 in WUrzburg as a satellite conference to the 11th Semiconductor Conference in Warsaw. The Conference in WUrzburg was con ducted in an informal atmosphere which was followed by three conferences, in WUrzburg in 1974 and 1976, and in Oxford in 1978. At the current Seminar the physics of magnetic materials was added to the scope of the Seminar, because high-field magnetism is also an important research area in the physics of high magnetic fields and is also one of the most active fields in physics in Japan. In the last decade, considerable effort has been devoted to develop the techniques for generating the high magnetic fields in many high-field labora tories in the world.