Book reviews Vogt, P.K.; Koprowski, H. (eds.): Retroviruses 2. Current Topics in Microbiology and Immunology, Vol. 107. Berlin, Heidelberg, New York, Tokyo: Springer 1983. vii+ 180 pp., 26 figs. Hard bound DM 96,-. Retroviruses have the potential to pick-up, recombine with, and transport cellular genes to distant sites. The five papers in this volume cover recent developments in research on retroviruses. In detail the papers demonstrate acute transforming feline retroviruses, analyze integration sites of endogenous retroviruses and their relationship to the vertebrate genome or their concern with the functions and distribution of o n c gene products in the cell. Many of these results are possible with the advent of recombinant DNA technology which now allows the study of molecular events surrounding the rearrangements of genetic material in eukaryotic cells. The papers provide new insights into some problems associated with artificially introducing genes into a vertebrate organism as well as a better understanding of cellular gene organization producing by evolution. H. St~iber, Berlin Vogt, P.K.; Koprowski, H. (eds.): Mouse Mammary Tumor Virus. Current Topics in Microbiology and Immunology, No. 106. Berlin, Heidelberg, New York, Tokyo: Springer 1983. vii+ 103 pp., 12 figs. Hard bound DM 58,-. The most extensively studied of mammalian retroviruses are those of murine origin, Since 1942 when Bittner demonstrated the identity between the milk-borne factor and the mouse mammary tumor virus (MMTV) this virus has became the prototype for B-type retroviruses. The present volume contains four critical reviews covering recent developments in research on this retrovirus....