The aim of this study was to investigate whether the profile of peripheral blood lymphocyte subsets of patients with high-risk malignant melanoma is associated with prognosis. Blood samples were systematically obtained from 31 patients with high-risk melanoma eligible for the Nordic Melanoma Cooperative Group adjuvant interferon study. The frequencies of peripheral blood lymphocyte subsets were monitored by flow cytometry using CD3, CD4, CD8, CD56, and CD69 monoclonal antibodies. Patients with low proportions of CD3+CD4+CD69+ cells and of CD3+CD56+ cells before treatment had an improved disease-free survival compared to those with high proportions [77.7 vs. 16.8 mo, hazard ratio (HR) 0.25, confidence interval (CI) 0.09-0.71, P=0.005 and 77.2 vs. 16.0 mo, HR: 0.25, CI 0.086-0.73, P=0.001, respectively]. Low pretreatment levels of these cell populations also correlated with a better overall survival (79.2 vs. 22.6 mo, HR: 0.17, CI 0.05-0.52, P=0.0005 and 78.2 vs. 21.4 mo, HR: 0.2, CI 0.07-0.59, P=0.001, respectively). In the multivariate analysis both the pretreatment proportion of CD3+CD4+CD69+ cells (P=0.01, HR: 0.21, CI 0.07-0.67) and CD3+CD56+ cells (P=0.01, HR: 0.22, CI 0.062-0.65) were independent prognostic factors for overall survival. Our data show that both the proportions of CD3+CD4+CD69+ cells and of CD3+CD56+ cells seem to have a prognostic potential in the natural course of melanoma. These results need to be confirmed in larger studies.