Many of the discoveries of multidrug resistance (MDR) have resulted from studies using drug-resistant cultured tumor cell lines as experimental models. To date, there has been no report on the detailed characterization of such a cell line from renal cell carcinoma (RCC). By long-term exposure of an established RCC (RCC8701) to increasing concentrations of adriamycin, we established a series of subcultures that were considerably more resistant to the cytotoxic effect of this drug. Biological morphology and cell cycles were analyzed by morphometry and flow cytometry. The chemoresistance index of cells were measured by methyl tetrazolium assay. For evaluation of the expression of MDR-related protein (MRP), mdr-1, glutathione transferase (GST-pi), and topoisomerase II mRNAs, the reverse transcription-polymerase chain reaction was used. Membranous expression of mdr-1-related p-glycoprotein was analyzed by immunofluorescence cytometry. The intracellular content of both glutathione (GSH) and glucose-6-phosphate dehydrogenase (G-6-PDH) were measured using a capillary electrophoresis method. Compared with parent cells, the resistant sublines had a slower growth rate and lower confluent density. They were smaller and mixed with giant cells in different sizes and with different numbers of nucleoli. Flow cytometric analyses showed that resistant cells had a greater percentage of cells in the G2/M phase. The resistant cells, RCC8701/ADR800, were 122 times more resistant to adriamycin and 238 times more resistant to epirubicin than the parent cells. The resistant cells also demonstrated cross-resistance to cisplatin and 5-fluorouracil. In addition to MRP, the contents of mRNA coding for mdr-1, GST-pi, and topoisomerase II in the MDR sublines were higher than in the native cell line. A higher content of cytoplasmic GSH and G-6-PDH were found in the resistant cells; however, the expression of the MDR-related membranous glycoprotein, p-glycoprotein, was not raised. The adriamycin-induced MDR sublines may be used as an experimental system for the search of a means to overcome drug resistance and elucidate possible mechanisms of acquired MDR involved in human renal cancer.