The present volume contains papers presented on the occasion of the Ichthyological Symposium on Genetics and Mutagenesis held on October 13 through 15, 1972 at the Biology Institute of the Association for Radia- tion and Environmental Research in Neuherberg near Munich, Germany. These symposia have been held annually since 1955 by former students of Prof. C. Kosswig and Prof. F. Anders in Hamburg or Giessen. In the last two years attendance has increased beyond the national German basis, but the Neuherberg meeting of fish geneticists was the first that could be called "international", the participants coming from twelve different countries. The organization of this meeting was made possible by the support of the Association for Radiation and Environmental Research, which provided the financial backing; special thanks are due to Min.- Rat. H. Costa and Dr. R. Wittenzellner. The scientific advice and encouragement of the Director of the Biology Institute, Prof. O. Hug, was also much appreciated, as was the helpful assistance of Dr. B. Betz and Dr. K. Gottel. In addition, I have to thank my colleagues and co- workers Mdmes. E. Neubner, I.S. Otten, and K. Peters, Messrs. M. Murr and M. Wiestner, and Dr. S. Holzberg for their help in organizing the meeting. Apart from the papers presented at the above symposium, we have in- cluded some papers by colleagues who were unable to attend the meeting.