We report 4 cases of sepsis-induced acute renal failure (ARF) with peculiar clinical presentation in which the renal biopsy was the only clue to a correct diagnosis. We observed 66 cases of ARF in a 4-year experience. Seven (11%) were associated with sepsis; in 3 of these (4.5%) a shock was present. Clinical picture of the remaining 4 cases (6%) was characterized by ARF with oligoanuria and proteinuria (> 2 g/L), fever, resistant to antimicrobial therapy, negative hemocultures and severe systemic symptoms. Such a presentation could suggest a non-infectious systemic disease; renal biopsies were carried out. Histological findings consisted of microabscesses of variable size in the interstitium and within the tubular lumina. A full-dose, broad-spectrum, i.v. antimicrobial therapy was started, with favourable outcome and recovery of renal function. Our clinical experience points out that the clinical picture of ARF in course of sepsis may be variable and that its relationship with septicaemia could not be readily discernible.