This study aims to correlate the most important prognostic factors of primary melanoma with sentinel node (SN) positive for metastases. We have enrolled 84 patients subjected to sentinel node biopsies for cutaneous melanomas of Breslow's thickness > or = 0.75 mm by using an intra-operative gamma probe after lymphoscintigraphy, without blue dye support. SN metastases were reported in 27% of cases (14% by histology and 13% by immunohistochemistry). By chi-square test Breslow's thickness > 2mm (p= 0.004), IV and V Clark's level (p= 0.02), ulceration (p= 0.05) and high mitotic rate (p= 0.05) were statistically significant (p < 0.05) with reference to SN positive for metastases, unlike the site of cutaneous melanoma, vertical growth phase, tumour infiltrating lymphocytes, regression and vascular invasion. Breslow's thickness remains the first prognostic factor to be considered for sentinel node biopsy in cutaneous melanoma, but other markers must be carefully estimated.