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Sentinel node biopay (s.n.b.) Ie now a well accepted way of managing patients presenting with high risk primary melanoma. The surgical technique has two major problems: I) the sentinel node (s.n.) In a lymph node station is not always close to the skin incision, necessitating a larger operative field. II) the lymphatic drainage can sometimes skip the first nodal station and, as a relult, the s.n. will be located in different lymph node regions. Percutaneous lymphoscintigraphy using 99m Tc labeled colloid has been shown to resolve both these problems but can not help to define the presence of microscopic metastases. we have now investigated eight patients following a protocol designed to detect preoperatively microscopic metastases in regional nodes. Six patients were clinical stage I and, except the inltial two patients of the series, all received both s.n.b. and percutaneous Iymphoscintigraphy, while two patients were stage II and received percutaneous lymphoscintigraphy only as positive controla. The percutaneous lymphoscintigrephy technique we developed differs from the standard technique as used an anti-melanoma labelled monoclonal antibody (185 99m Tc F(ab 1 ) 2 MoAbs 255.28S. Sorin Biomedica) instead of a non specific radiotracer like colloid. An equal amount of rediotracer was also injected in the contralateral side as a control. Dynamic images were acquired for the first 5 minutes after Injection, followed by static views at 10, 15, 30 minutes and 1, 3, 24 hours post injection. In all six patients studied with percutaneous lymphoscintigraphy the s.n. was easily visualized at least 15 minutes after injection of the radiotracer. In four cases no stained lymphatic vessels and nodes were found during s.n.b.: of these, three received percutaneous lymphoscintigraphy and two presented microscopic metastases on the nodes biopsied following the findings of percutaneous lymphoscintigraphy only. To date, one false negative s.n. has been recorded: this was the first patient of the series,. who developed clinically evident nodal metastases 9 months after the s.n.b. This is one of the two patients who did not receive preoperative percutaneous lymphoscintigraphy. Finally, the differences found with percutaneous imrnuno-lymphoscintigraphy did not show a specific result linked to the presence of F(ab 1 ) 2 in radiotracer uptake between both sides on each patient, whether the patients were stage I or stage II. There were no complications following percutaneous lymphoscintigraphy. This pilot study demonstrates that percutaneous lymphoscintigraphy is a safe and effective method of detecting the s.n.