In the National Cancer Institute and S Pio X Hospital series we registered 981 patients with primary cutaneous melanoma and no evidence of clinically detectable regional node metastases underwent sentinel node (SN) dissection to microscopically define the tumor status of the regional lymph nodes. In 62.2% of cases, only one SN was detected; 26.4% of patients had two SNs and 11.4% had three or more SNs. A positive SNB was demonstrated in 18.1%. Analysis of survival indicated that the tumor status of the nodes was the most important prognostic factor. Breslow's thickness had a significant impact on survival in tumors of 4 mm or thicker, and ulceration dropped to a borderline significant P-value. To assess the tumor burden in positive SNB, all slides (148 SN pos) were reviewed. Twenty per cent of these patients had evidence of metastasis in other nodes. Of the remaining 80% with a single tumor-involved SN, 62% had a single metastatic deposit. Preliminary data from this study indicate that several subgroups may be identified among patients with 1 positive node, but adequate analysis of survival requires a larger number of patients and a multicentric study.