A clinical relationship between dose-intensity of melphalan and response rate has been demonstrated in multiple myeloma. Promising results have been reported after 200 mg/m(2) melphalan, especially in younger patients. It is uncertain whether 100 mg/m(2) melphalan (MEL100) can offer similar results in older patients. To address this issue, patients were treated with 2 or 3 MEL100 courses followed by stem cell support. Seventy-one patients (median age, 64 years) entered the protocol at diagnosis. Their clinical outcome was compared with that of 71 pair mates (median age, 64 years) selected from patients treated at diagnosis with oral melphalan and prednisone (MP) and matched for age and beta2-microglobulin. Complete remission was 47% after MEL100 and 5% after MP. Median event-free survival was 34 months in the MEL100 group and 17.7 months in the MP group (P <.001). Median overall survival was 56+ months for MEL100 and 48 months for MP (P <.01). In a multivariate analysis, beta2-microglobulin levels and MEL100 were independent risk factors associated with outcome: superior event-free and overall survival were observed in patients presenting low beta2-microglobulin levels at diagnosis and receiving MEL100 as induction regimen. In conclusion, MEL100 was superior to MP in terms of complete remission rate, event-free survival, and overall survival.