This study examines the response to dexamethasone-doxorubicin-vincristine (DAV) therapy, followed by conditioning regimen and autologous stem cells transplantation (ASCT) in patients with multiple myeloma in relation with the presence of polymorphisms in genes involved in drug metabolism (GSTP1) and DNA synthesis (TYMS). GSTP1 G313G genotype (OR=5.49; 95% CI, 1.3-22.5, p=0.02) and TYMS A227A genotype (OR=3.41; 95% CI, 1.3-8.9, p=0.01) resulted significantly associated with a poor response following chemotherapy and the risk increased for the combined genotype (OR=13.54; 95% CI, 2.0-91.3, p=0.01). TYMS T157T genotype was significantly associated with a poor response after ASCT (OR=4.60; 95% CI, 1.2-16.9, p=0.02). Pre-therapeutic individual determination of the GSTP1 and TYMS polymorphisms could help in choosing the most appropriate protocol.