Multiple myeloma (MM) represents a cancer with one of the worst overall survival statistics. While the mainstay treatment for patients with MM is a combination of the drugs melphalan and prednisone, cure is extremely rare. The major obstacle for curing MM is drug resistance, whereby MM cells become resistant to melphalan. In order to enhance the effectiveness of currently available chemotherapeutic drugs, we must understand how MM cells become resistant to therapy. The goal of this proposal is to utilize a viral system to know out melphalan-resistance genes. This approach will lead to a better understanding of melphalan resistance.