The current roles and controversies in imaging of the kidneys for the evaluation of patients with acute renal infection are reviewed. The nomenclature used in describing the extent of the renal imaging findings in acute pyelonephritis suggested by the Society of Uroradiology to help avoid confusion in terminology in the past literature is briefly described. Computed tomography (CT) is superior to urography and renal sonography for the evaluation and management of adults with acute renal infection. [99mTc]-dimercapto succinic acid (DMSA) cortical scintigraphy is the imaging study for the evaluation of children with acute pyelonephritis investigated by some, although power Doppler ultrasound, and even CT, can be considered as a possible alternative.