DNA amplification on chromosome 20q13 is commonly detected in breast cancer and correlates with poor prognosis. Definitive critical target genes on this amplicon have however, not yet been identified. We describe in this paper isolation of a novel gene named BTAK, encoding a putative member of protein serine/threonine kinase family localized on chromosome 20q13 that is amplified and overexpressed in breast tumor cell lines. BTAK maps close to the critical region of amplification defined earlier on this amplicon. Deduced amino acid sequence shows conservation of all the subdomains predicted in protein kinase super family. Translated BTAK peptide shows significant homology with previously cloned protein serine/threonine kinase encoding genes Ip11 from S cerevisae and aurora from Drosophila, both shown to be functionally involved in normal chromosome segregation process. Our findings suggest that amplification and overexpression of BTAK may be playing a critical role in oncogenic transformation of breast tumor cells.