Primary plasma cell leukemia (PPCL) is a rare form of disease accounting for 1-2 percent of myelomas. Between September 1990 and November 2000, among 540 patients with myeloma studied, 24 fulfilled the criteria of PPCL (4.4 percent). We found high frequencies of female patients (62 percent), Bence Jones proteinuria (79 percent), anemia (88 percent), bleeding (54 percent), confusional syndrome (42 percent), weight loss (71 percent), hepatomegaly (25 percent), splenomegaly (21 percent), leukocytosis (62 percent), and thrombocytopenia (71 percent). High serum levels of creatinine, calcium, lactate dehydrogenase (LDH), and beta(2)-microglobulin were detected in 50 percent, 37 percent, 58 percent, and 71 percent, respectively. Four patients were treated with vincristine, melphalan, cyclophosphamide, prednisone, and adriamycin (VMCPA), 12 with vincristine, adriamycin, and dexamethasone (VAD), and 8 with M-80 (oral melphalan 80 mg/m(2) plus dexamethasone 40 mg/m(2)). There was a trend toward lower values of Karnofsky score (P=0.07) and higher values of LDH (P=0.2) in the VAD group. Other clinical characteristics were comparable among the three groups. Complete plus partial responses were achieved in one and six patients treated with VMCPA and M-80, respectively. All patients treated with VAD failed to respond to treatment. Patients receiving the M-80 regimen experienced higher platelet toxicity (P=0.05), vomiting (P<0.0003), and mucositis. Also, the need for red blood cell transfusions was higher in the M-80 group. Median overall survival was 60 days. Overall survival was better in patients achieving complete or partial response. In conclusion, our study illustrates that intermediate doses of melphalan plus dexamethasone are an effective chemotherapy regimen for this aggressive disease. Response to treatment is the only prognostic factor for survival in these patients.