Multiple myeloma (MM) represented 14% of new haematological malignancies in the US in 2003 and almost 19% of anticipated deaths. Treatment with standard chemotherapy has resulted in a median survival of about 3 years and despite the improvements in survival seen with the use of intensive therapy supported by autologous stem cell transplantation, MM remains incurable; hence, new therapeutic strategies are urgently needed. One novel approach to the treatment of MM is the use of proteasome inhibitors. Proteasomes are ubiquitous protease complexes involved in diverse aspects of cell biology, such as protein homeostasis, cell cycle progression, apoptosis and inflammation, as well as resistance to antineoplastic therapy. The first-in-class proteasome inhibitor, bortezomib was recently approved in the US for the treatment of patients with MM who have received at least two prior therapies and are progressing on their last therapy. Its use in earlier-stage MM, other haematological malignancies and in solid tumours as monotherapy and in combination therapy is currently under investigation.