Acute multifocal bacterial nephritis is a severe form of acute renal infection in which heavy leucocytic infiltrates occurs throughout kidney. Therefore, in contrast to uncomplicated acute pyelonephritis, it frequently causes acute renal failure. We here report an unusual case of acute multifocal bacterial nephritis which caused acute real failure and massive proteinuria. A 44-year old man was referred to our hospital because of high fever and both flank pain and non-oliguric acute renal failure. He had pyuria and massive proteinuria(5.87g/day), and serum creatinine level of 3.6mg/dL. We initially suspected hemorrhagic fever with renal syndrome. But immunofluorescent antibody for Hantavirus was negative and E. coli was isolated at urine. Computed tomography showed multifocal areas of wedge-shaped low densities in both kidneys. Kidney biopsy revealed tubulointerstitial infiltration of leucocyte without glomerular change. After treatment of antibiotics, proteinuria completely disappeared and serum creatinine level decreased to 1.0mg/dL. (Korean J Med 57:375-379, 1999)