A case study is reported using patent blue violet entrapped in liposomes to localize lymph nodes before surgery. Liposomes containing 44 mg patent blue violet were injected into foot lymphatics of a patient due to undergo retroperitoneal staging-lymphonodectomy. Lymph nodes were readily visualized and removed, and urine and serum was collected for assay of the dye. The maximum concentration of patent blue violet in serum was 2.7 micrograms mL-1, 1.5 h after the termination of the injection, almost no dye was detectable by the time of the operation 24 h later. In the first urine sample (2 h after the termination of the injection) the concentration of patent blue violet was 1.3 micrograms mL-1, and subsequently diminished, with the last urine sample to contain detectable dye being collected 20 h later. A total of 0.8 mg dye (2% of the injected amount) was excreted in the urine suggesting 10% of the circulating amount of dye was renally excreted. Endolymphatic injection of patent blue violet simplifies the often difficult process of finding the lymph nodes and additionally reduces side-effects. All surgery cases demanding a radical lymphonodectomy may profit, including testicular or bladder cancers and many gynaecological tumours.