The application of technologies such as DNA microarrays and the ongoing human genome sequencing project will help the study of the genes underlying the pathogenesis of cancer. Chromosome 11q22–23 is frequently deleted in human solid and lymphoid neoplasms, such as breast and colorectal cancer, chronic lymphocytic leukemia and mantle cell lymphoma. Thus several cancer genes are likely to map to this region. To analyze the deletions in lymphoproliferative disorders, a PAC/BAC contig of chromosome 11q22–q23.3 was constructed, using as a guide the yeast artificial chromosome contig previously applied to characterize the deletions in patients affected by Jacobsen syndrome. BAC and PAC clones were identified and localized by screening of different human genomic libraries using the polymerase chain reaction, filter hybridization and database searches, using sequence-tagged sequences, expressed sequence tags or gene sequences known to map to the region of interest. The PAC and BAC end sequences were then used as new sequence-tagged sequences for database analysis or to design polymerase chain reaction primers after eliminating the repetitive elements using BLAST software. The assembled PAC/BAC contig stretches from D11S1897 to FRA11B. Construction of a transcript map to identify possible cancer genes is continuing. The ordered genomic clones will be used to analyze DNA samples of lymphoid tumors to determine regions of chromosome loss or amplification within the region of the contig using DNA microarray technology or the Invader assay.