Emphysematous pyelonephritis (EPN) is a rare necrotizing infection of the kidney caused by gas-forming organisms, usually occurs in diabetic patients, and often requires nephrectomy for effective therapy. EPN is rarely reported in renal allografts, with only 20 cases found in the English literature. We report herein a case of EPN in a transplanted kidney resulting in acute renal failure and sepsis. The patient was managed non-operatively with subsequent recovery of renal allograft function. Based on this experience and a review of the literature, we suggest an amended classification system for EPN in kidney transplantation to plan and guide treatment options accordingly. However, the scarcity of this disease process, coupled with the lack of prospective validation of the new classification scheme, prevents drawing definitive conclusions regarding optimal management strategies including the role and timing of allograft nephrectomy. © 2010 John Wiley & Sons A/S.