Pharmacogenetics achievements concerning the problem of multidrug resistance in chemotherapy started to be more frequently used in contemporary oncology to improve the treatment efficacy by individual approach to the patient. Disturbed trans-membrane transport of chemotherapeutics is one of the most important mechanisms of chemo-resistance, which seems to depend on the drug resistance genes expression (MRP1, LRP, BCRP). Between them, polymorphisms of MDR1 gene coding trans-membrane transport glicoprotein P-gp have been reported to affect the outcome of therapy, and was studied for different drugs-digoxin, fexofenadine, etoposid, vincristine, vinblastine, athracyclines and taxans. It seems that genotyping of multidrug resistance genes and identifying specific haplotypes can become an important tool in predicting individual sensibility to chemotherapy.