Contrast-enhanced CT and MR imaging of the kidney were performed in two patients with acute renal failure and severe loin pain following a track race. Prior to the exercise both patients had had flu-like symptoms and took oral medications. There was no evidence of myoglobinuria. Immediate postcontrast CT of the kidney showed multiple patchy areas of poor contrast enhancement; after 24 h, there were multiple patchy enhancing cortical areas on CT without further use of intravenous contrast media. Magnetic resonance imaging of the kidney showed patchy areas of high signal intensity with obliteration of the corticomedullary contrast on T1-weighted images. On T2-weighted images the signal intensity of the lesion was high in one patient and low in the other.