Regulatory T cells (Tregs) have been implicated as inhibitors of antitumor immune reactions. However, data on the relevance of their prevalence at tumor sites in influencing disease outcome are controversial. The aim of our study was to investigate the role in tumor progression and the prognostic impact of the density of lymphocytes expressing FOXP3, a transcription factor expressed predominantly by CD4(+)CD25(+) Tregs, in primary cutaneous melanoma. We examined the infiltration of FOXP3(+) cells by immunohistochemistry in tumor samples from 97 patients and evaluated in relation to patient and tumor parameters. The degree of infiltration by FOXP3(+) cells did not show correlation with the thickness of melanomas. Moreover, no associations were found with metastasis formation during the 5-year follow-up period, patient survival, or any other clinicopathologic parameters studied. These results suggest that the presence of FOXP3(+) lymphocytes in primary tumors is not of prognostic importance in human cutaneous melanoma.