We developed two leukemic cell lines (K562 HHT and L1210 HHT) stably 16.7 fold and 13.4 fold resistant to HHT respectively with which the culture were treated. Both cell lines were also cross-resistant to DOX, VCR, DNR and Mel. Increased expression of MDR1 gene in the both lines was noted. To further evaluate the implications of MDR1 in HHT resistance. We studied the expression of MDR1 in sensitive and HHT-resistant sublines of K562 by ABC with an monoclonal antibody against P170, JSB-1. K562 HHT cells were positive but sensitive cells were negative. Additionally, the increased drug resistance was associated with increased level of expression of alpha and pi class GST gene, but not with increased level of expression of mu class GST gene.