A phase 2 trial was performed to study the combination of bortezomib (VELCADE) with intermediate-dose dexamethasone (DEX), and continuous low-dose oral cyclophosphamide (CY) in patients with relapsed multiple myeloma (MM). Fifty-four patients with advanced MM were enroled to receive eight 3-week treatment cycles with bortezomib 1.3 mg/m(2) on days 1, 4, 8, and 11, followed by three 5-week cycles with bortezomib 1.3 mg/m(2) on days 1, 8, 15, and 22. Within all cycles, DEX 20 mg/d was given orally on the day of bortezomib injection and the day thereafter. In addition, patients received CY continuous oral treatment at a dose of 50 mg/d p.o. once daily. Fifty patients completing at least one treatment cycle were evaluable for response. Complete, partial, and minor responses occurred in 16%, 66% and 8% of patients, respectively; overall response rate 90% (efficacy analysis). Median event-free survival was 12 months, with a median overall survival of 22 months. Adverse events (AE) of grades 3 or 4 occurring in at least 10% of patients comprised leucopenia, infection, herpes zoster, thrombocytopenia, neuropathy and fatigue. Bortezomib combined with DEX and CY is a highly effective treatment for relapsed MM at an acceptable rate of grade 3/4 AE. Antiviral prophylaxis appears to be mandatory.