The leukemias have long been associated, albeit rarely, with the development of renal failure and several metabolic perturbations. While renal insufficiency may result from a variety of mechanisms in the setting of leukemia, severe leukostasis with microvascular insufficiency and renal parenchymal infiltration by blast cells are rare and infrequently described etiologies. In addition, hypokalemia can occur from lysozyme-induced renal tubular injury with inappropriate kaliuresis. We present a case of acute myelomonocytic leukemia that was complicated by renal failure and severe hypokalemia and discuss the probable mechanisms.