Proteasome inhibitors, a novel class of chemotherapeutic agents, enhance the antitumor efficacy of anthracyclines in vitro and in vivo. We therefore sought to determine the maximum tolerated dose (MTD) and dose-limiting toxicities of bortezomib and pegylated liposomal doxorubicin (PegLD). Bortezomib was given on days 1, 4, 8, and 11 from 0.90 to 1.50 mg/m2 and PegLD on day 4 at 30 mg/m2 to 42 patients with advanced hematologic malignancies.