Nephrological diseases--in special cases also unsettled forms of microhematuria--require a biopsy of the kidney. To date this intervention has mostly been performed under x-ray control by means of the Menghini or the Trucut-needle. Ultrasound opened up new perspectives, particularly after the introduction of perforated ultrasound probes. These ensure complete control of the intervention provided that appropriate puncture systems are applied. The cut biopsy needle (Otto) offers great advantages because it is thinner than the puncture systems used so far. With identical quality of the cast compared to that obtained with conventional techniques, the needle recommended is less traumatic and hence both risk and patient discomfort are reduced. Report on 52 punctures.