Transcutaneous fine needle biopsy of retroperitoneal lymph nodes after lymphography minor is connected with only discomfort for the patient. It is used for clarification of a possible infestation of metastases by malignant growth, the lymphatic drainage of which is situated retroperitoneally. A new instrument for puncture is presented, the use of which permits increase in accuracy of impact and reduction of radiation exposure for both patient and examiner. These advantages are of great importance, especially in serial puncture of several lymph nodes along the lymphogenous pathway of metastases. The quality of the fluoroscopic picture is even improved by the instrument for puncture.