Acute kidney injury is a rare but important complication of nephrotic syndrome. We demonstrated here nine patients with nephrotic syndrome and oliguric renal failure in Siriraj Hospital during 2007-2009. Renal biopsy was done in every patient. The results were focal and segmental glomerulosclerosis (FSGS) in three patients, minimal change disease in four patients and collapsing focal segmental glomerulosclerosis in two patients. Seven patients had dramatic response to corticosteroid treatment within a few weeks and had rapid recovery of renal function. The exact mechanism of idiopathic renal failure is not well understood but it might be related to reduction in ultrafiltration coefficient of the glomeruli.