High magnetic fields have been an important tool in semiconductor physics for a long time. The area has been growing very rapidly since quantum effects in silicon field-effect transistors have become of practical interest. Since the discovery of the quantum Hall effect by Klaus von Klitzing in 1980, this subject has grown exponentially. The book contains 42 invited papers and 37 contributed papers which were presented at the 7th of the traditional Würzburg conferences. For the area of high magnetic fields applied in semiconductor physics recent results are discussed, and the state-of-the-art is reviewed. More than 50% of the papers concern two-dimensional electronic systems. Other subjects of current interest are magneto-optics and magneto transport in three-dimensional semiconductors. Special attention has been paid to the rapidly growing field of semimagnetic semiconductors.