AG 99 is a potent inhibitor of EGF receptor tyrosine kinase with IC50 value of 10 μM .AG 99 is a potent and competitive EGFR tyrosine kinase inhibitor against both the substrate polyGAT and ATP . In serum-starved human bladder carcinoma cell line 5637 cells, the 145-kDa protein, which was the β-subunit of c-Met/hepatocyte growth factor (HGF) receptor, was phosphorylated on 1003, 1234 and 1235 tyrosine residues. Also, tyrosine kinases EGFR and Src were activated. While, AG99 or inhibitors of Src (PP2, SU6656) significantly inhibited tyrosine phosphorylation of p145met and induced cell death through activation of caspase-like proteases. These results suggested that serum-independent growth of 5637 cells was involved by the tyrosine phosphorylation of p145met mediated by Src and EGFR.