We report a case of a Chinese woman who presented with multiple myeloma and acute renal failure due to cast nephropathy, with an extremely high serum lambda free light chain concentration. She was successfully treated with chemotherapy and high cut-off extended haemodialysis. High cut-off haemodialysis is a new treatment modality which can achieve rapid free light chain clearance. This may contribute to a better renal outcome and overall prognosis for patients with multiple myeloma.