E.B. Kopp and S. Ghosh, NF-kB and Rel Proteins in Innate Immunity; D.T. Weaver, V(D)J Recombination and Double-Strand Break Repair; P. Kisielow and H. von Boehmer, Development and Selection of T Cells: Facts and Puzzles; G. Kroemer, The Pharmacology of T Cell Apoptosis; G.-K. Sim, Intraepithelial Lymphocytes and the Immune System; B.A. Imhof and D. Dunon, Leukocyte Migration and Adhesion; G. Dranoff and R.C. Mulligan, Gene Transfer as Cancer Therapy; Subject Index; Contents of Recent Volumes.