In the last years there has been an arising concern in the sentinel lymph node identification, the first lymph node to receive direct draining from the primary tumour, specially in malignant melanoma (MM). We studied 20 patients with MM: 10 with palpable regional lymph nodes and 10 without palpable LN by performing a lymphoscintigraphy using 99mTc-nanocolloid and a gamma-ray detecting probe during the surgery to locate the sentinel lymph node. In patients with palpable LN, 13 sentinel lymph nodes were identified. Ten of them were MM involved. Furthermore, 82 LN were harvested from involved lymph basins and 30 of them were positive for MM. In patients without palpable LN, 14 sentinel lymph nodes were identified (3 positives and 11 negatives for MM) and other 76 LN were resected (all of them negative). There were not <<skip metastases>> in any patient. These preliminary results support the utility of the technique for the diagnosis and lymphadenectomy selection in patients without palpable LN but which could be involved by micrometastases.