NCI-H69/CPR is a drug resistant subline of NCI-H69. Drug resistance was developed by addition of a stepwise increase in cisplatin to the growth medium of the parental line. The cell line exhibits a 5-fold resistance to cisplatin and is cross resistant to melphalan. A significant change in cellular glutathione content or sensitivity to cadmium chloride (as indicator of metallothionein content) was not detected, but changes in glutathione-S-transferase activity were seen. Cisplatin accumulation was unchanged compared with the parent line. It is recommended to culture the cells without drugs after resuscitation until the first passage.