Statins, like simvastatin, inhibit the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, which catalyzes the conversion of HMG-CoA to mevalonate. Interestingly, in MM models statins induce apoptosis, inhibit proliferation, overcome primary and secondary drug resistance, and synergize with cytotoxic drugs. Oligonucleotide microarray analyses demonstrated that de novo and acquired drug resistance are associated with an increase of HMG-CoA reductase gene expression. We have shown before that adhesion of MM cells to bone marrow stromal cells mediates strong multidrug resistance and that this can be overcome by co-treatment with simvastatin in non-toxic concentrations. Interestingly, statin induced apoptosis in MM cells is not hampered by adhesion to bone marrow stromal cells.