The proteasome is primarily responsible for intracellular protein degradation. The abnormality of its activity is sign of tumorigenesis. It was confirmed that proteasome inhibitors have activities against a variety of malignancies. Bortezomib, the first proteasome inhibitor, obtained permission of clinical trial and on sale. Multiple myeloma patients treated with bortezomib have gained a high overall response rate and complete remission rate. A lot of studies on effects of proteasome inhibitors on leukemias, including plasma cell leukemia; chronic lymphocytic leukemia, adult T cell lymphoma/leukemia, chronic myeloid leukemia and acute myeloid leukemia, were reviewed in this article.