We report the construction of a YAC library that provides 10-fold redundant coverage of the chicken genome. The library was made by transforming S. cerevisiae AB1380 with YAC constructs consisting of partially digested and size fractionated (>465 kb) EcoRI genomic fragments ligated to pCGS966 YAC vector arms. The primary library provides 8.5-fold redundant coverage and consists of 16,000 clones arrayed in duplicate 96-well microtiter plates and gridded on nylon membranes at high density (18,000 clones/484cm2). The average insert size, 634 kb, was derived from size fractionation of a random sample of 218 YACs. Hybridization of five unlinked chicken genes to colony blots revealed six or more positive clones. This is consistent with the theoretical expectation from average insert sizes and number of clones. A second collection of clones consists of a further 20,000 colonies, of which 20% contain inserts larger than 450 kb and 80% contain only coligated vector arms. We estimate that these clones provide a further 1.5-fold redundant coverage of the chicken genome; thus, the total collection of 36,000 clones provides 10-fold redundant coverage of the chicken genome. The library is intended as a resource for fine-scale analysis of the organization of the chicken genome and is presently being used to construct a contig map of chicken Chromosome (Chr) 16, which contains the MHC and nucleolar organizer.