A set of over 25 000 unique cDNAs from zebrafish is now available. Zebrafish is an excellent model system for studying a broad range of processes in vertebrates, from development to hematopoiesis. The zebrafish genome is roughly half the size of the human genome, and identification of genes in zebrafish could help identify protein-coding regions in humans by comparative genomic methods. A limiting factor for identification of genes is the availability of a normalized and non-redundant cDNA libraries. A collaboration between the Max-Planck Institute for Molecular Genetics, Berlin, and Washington University, St. Louis, used 223 oligonucleotides in hybridization experiments to generate a ‘fingerprint’ for each of 75 000 clones from zebrafish embryonic and adult liver cDNA libraries. This method, dubbed ‘oligonucleotide fingerprinting,’ is believed to be superior to several other methods currently employed to normalize libraries. Using this method, the initial set of clones was clustered into 25 102 cDNAs that are expected to be minimally redundant. These clones are freely available as glycerol stocks, filter sets or as individual clones. (Clark, M.D. et al. Genome Res. [in press]) AP