Cover photograph (Copyright © 2005, American Society for Microbiology. All Rights reserved.): The most common chromosomal translocation among all human cancers is t(14;18). Fluorescence in situ hybridization illustrates this translocation (courtesy of Marilyn Slovak, City of Hope, CA). The location of the immunoglobulin heavy chain locus is shown in green, and the location of the bcl-2 locus is shown in red. The chromosomal translocation results in derivative chromosomes der(14) and der(18), which position the immunoglobulin and bcl-2 loci adjacent to one another. The related article desribes why the bcl-2 major breakpoint region is fragile and how the rejoining of the breaks occurs. (See related article on p. 6475.)