Abstract : From loss of heterozygosity (LOH) studies, it has been determined that three regions 17p13, 17q12-22, and 17q24-25 of human chromosome 17 are frequently deleted in breast cancer. The presence of LOH in these region suggest the location of putative tumor suppressor. Our research is focused on the isolation of chromosome 17 genes. A method for the isolation of chromosome specific cDNAs using high density arrayed cDNA and chromosome specific cosmid libraries was developed. To date we have isolated and mapped 105 unique cDNAs of chromosome 17. Of these we have mapped 72 of these cDNAs to the three regions that have been determined to be associated with LOH in breast cancer. These cDNAs are now potential candidate genes for the putative tumor suppressor associated with breast cancer on human chromosome 17. Potential function of these cDNAs will be determined by comparing sequence information to known protein motif in the genome data base. Genes encoding for proteins involved in cellular functions including signal transduction, transcription and cell cycle pathways are prime candidate for tumor suppressor. These genes will be further characterize to determine if they play any role in breast cancer etiology.