Long-term survival patients with acute and severe renal failure due to multiple myeloma. We selected 37 cases, followed-up for more than 36 months or until death, from a series of 45 patients affected by acute renal failure due to multiple myeloma in order to identify the parameters that could allow the outcome to be predicted. The patients were allocated to group 1, consisting of 27 patients who died within one year and to group 2, consisting of 10 patients who survived for more than 36 months. Renal failure was severe enough to require dialysis in 28 patients, 16 of whom were oliguric. Renal biopsy was performed in 23 cases, whereas light chain isoelectric point and serum beta 2-microglobulin levels were evaluated in each patient. All the patients underwent chemotherapy, which was associated with plasma exchange in 16 patients. Statistical analysis of the potential prognostic factors in the 2 groups showed that the incidence of hypercalcemia, infection, irreversible renal failure and severe tubulo-interstitial damage was significantly higher in group 1. Sex, tumor load, severity of renal failure and light chain isoelectric point had no prognostic significance. Finally, the number of patients treated by plasma exchange was significantly higher in group 2. Our results underline the prognostic role of both hypercalcemia and infection and justify aggressive treatment consisting of chemotherapy, plasma exchange and dialysis, even in cases of severe renal failure and high tumor load. 