In recent years ultrasonography has been established as a reliable diagnostic method in various urological disorders. The first and most important indication is the differentiation between renal cysts and solid tumors. But ultrasound is suitable, too, for the diagnosis of haematomas, abscesses and hydronephrosis in the postoperative period and for the evaluation of renal transplants to detect early signs of rejection. Ultrasound allows the examination of patients with renal insufficiency and of patients with unilateral absence of contrast medium excretion in urography, because it is independent of contrast medium and renal function. In these patients as well as in traumatized patients ultrasound can be used as a bed-side method. Furthermore, it is possible to diagnose retroperitoneal tumors causing obstruction, megaureter, and tumors of the bladder. For the diagnosis of the prostate the rectal application of an ultrasonic transducer seems to be the best method. With an ultrasonic Doppler probe the diagnosis of testicular torsion is possible on ground of the absence of intratesticular arterial pulsation. Finally the possibility of ultrasonic targeted percutaneous puncture of the kidneys, tumors and cysts as a diagnostic and occasionally therapeutic approach has to be mentioned.