Principal signs and symptoms of renal parenchyma infections are discussed in relation to findings in 10 cases. Disorders studied were acute pyelonephritis and focal and bacterial acute nephritis, renal abscess and perinephritic phlegmon. Intravenous urography was only moderately sensitive (4/7) and of little specificity. Ultrasound imaging showed much greater sensitivity (8/10), undetected lesions being the earliest cases of severe acute pyelonephritis. The scanner was the most sensitive investigatory method since it associated anatomical and functional aspects in data obtained, justifying its initial use for certain authors.