The accuracy of ultrasonography in the diagnosis of different pathological renal conditions is evaluated. Correlations were established to the findings on intravenous urography and selective angiography. Ultrasonography is suitable for the determination of the exact size and site of the kidney and, therefore, should be used routinely in the follow-up of renal transplant recipients. The ability to differentiate between solid and cystic lesions is of partcular value. Moreover, perirenal changes are easily recognizable. The limits of B-mode sonography lie in the interpretation of central expanding lesions with a diameter of under 3 cm. This non-invasive method should be used selectively in the diagnosis of renal disease, whereas angiography should be limited to the classification of equivocal ultrasound findings and in the case of solid tumours.