Bortezomib (formerly PS-341), a promising new drug for the treatment of multiple myeloma, recently received accelerated approval from the U.S. Food and Drug Administration (FDA) for the therapy of patients with progressive myeloma after previous treatment. Two phase II studies of bortezomib used the same schedule of twice-weekly i.v. dosing for the first 2 weeks of each 3-week cycle. In a randomized study of 54 patients, two doses were compared (1.0 and 1.3 mg/m2) and objective responses occurred at both dose levels (23% versus 35%), including one complete response in each arm. In the other phase II study, 202 heavily pretreated patients (median of six prior therapies) all received the same schedule at 1.3 mg/m2. Of 188 evaluable patients, complete responses occurred in five (3%) and partial responses occurred in 47 (25%). The median duration of response was 365 days. The most clinically relevant adverse events were asthenic conditions, nausea, vomiting, diarrhea, thrombocytopenia, and a peripheral neuropathy that often was painful. This report highlights the FDA analysis supporting the accelerated approval.