Artefacts or not completely visualised renal contours can lead to the erroneous diagnosis "renal tumour". This false diagnosis is mostly avoidable by means of accurate examination technique. Further radiological examination will be required only in exceptional cases. Incompletely visualisable parenchymal ridges with socalled incomplete multiple kidneys frequently create the impression of an intrarenal tumour and indicate the need for further clarification. There is a relatively high degree of uncertainty in intrarenal space-occupying processes below 2.5 cm diameter, as far as structural analysis is concerned. In such cases, provided a sufficiently strong clinical and roentgenological suspicion is sustained, angiography and, if necessary, exposure, should be recommended on a rather liberal basis.