Objective:To evaluate the correlation of doxorubicin and cisplatin intervention with the expression levels of MDR1 and MRP1 in anaplastic thyroid carcinoma cell line HTh74. Methods:Doxorubicin resistant cells (HTh74/DOX) and cisplatin resistant cells(HTh74/DDP) were obtained by treating the HTh74 cell with doxorubicin or cisplatin for 6 months respectively. Fluorescent quantitative RT-PCR was adopted to detect the transcription of MDR1 and MRP1 in HTh74/DOX and HTh74/DDP. Results:Compared to their parental HTh74 cell,HTh74/DOX cell expressed high level of MDR1 and low level of MRP1,HTh74/DDP expressed high level of MRP1 and low level of MDR1. HTh74/DOX cells lacked cross resistance to cisplatin,and HTh74/DDP cells lacked cross resistance to doxorubicin. Inhibitors of MDR1 or MRP1 partly restored the toxicity of doxorubicin or cisplantin on the resistant cells respectively. Conclusion:Different chemotherapeutics increase the expression of different ABC transporters to enhance the drug resistance. Detecting the expression of ABC transporters can be used to predict the effect of chemotherapeutic drugs in clinical. The proportionate inhibitor of ABC transporter combined with chemotherapeutic drugs may be effective in individual treatment.