Two cell lines, SNK57 and NKB1, were established from human bladder cancer: SNK57 from a transitional cell carcinoma (TCC) in a 73-year-old female and NKB1 from a residual TCC following MEC (methotrexate, farmorubicin and cisplatin) chemotherapy in a 64-year-old female. Doubling time of SNK57 and NKB1 cells was 24 hours and 45 hours, respectively. The chromosome number of both cell lines was 100 percent anueploid with a mode of 43 chromosomes for SNK57 and 107 for NKK1. Both SNK57 and NKK1 induced tumors at the site of subcutaneous injection of nude mice. Histology of the tumors closely resembled that of the original ones from which they were derived. Although NKB1 was 4 times more resistant to doxorubicin (ADM) as compared to SNK57, overexpression of MDR1 gene product, P-glycoprotein was not evident in NKB1 as well as SNK57. These two new cell lines with different chemosensitivity to ADM may be a useful model for developing new chemotherapeutic strategies for human bladder cancer.