Three novel taxinine analogues were prepared and tested for their activity as multidrug resistance (MDR) reversal agents in comparison with verapamil. In vitro testing demonstrated that compounds 8-10 possess MDR-reversal activity in the KB/V cell line. Half-hour after treatment with 5, 10, and 20lmol/L compound 9, the intracellular rhodamine123 concentration increased 2.3, 2.9, and 3.2-fold, respectively, higher than 1.88-fold of 10lmol/L verapamil in KB/V cell line. In vivo studies with VCR-resistant KB/V tumor xenografts showed that compound 9 in combination with VCR significantly inhibited tumor growth. Treatment with VCR or 9 alone did not result in growth inhibition. These results reveal that three taxinine analogues are good modifiers of MDR in tumor cells.