['Nonneoplastic mononuclear cells commonly infiltrate lesions of mycosis fungoides.', 'We sought to determine the immunophenotypic characteristics of these cells and to determine whether the presence of CD8+ tumor-infiltrating lymphocytes has an impact on prognosis.', 'Skin biopsy specimens from 78 patients were stained with immunopleroxidase techniques to determine their phenotypic characteristics. The proportion of CD8+ tumor-infiltrating lymphocytes was quantified and compared with stage of disease and survival rate.', 'Patients with more limited T-stage disease tended to have a higher proportion of CD8+ cells in their skin biopsy specimens, compared with patients with more advanced T-stage disease. Within each T-stage patients with a larger proportion of CD8+ cells had a better survival rate than those with fewer CD8+ cells (p < 0.05 for T1 and T3). A multivariate analysis confirmed the importance of T stage (p = 0.0006), overall stage (p = 0.0112), and CD8 positivity (p = 0.0335) in this cohort of patients.'] Do cD8-positive tumor-infiltrating lymphocytes influence the long-term survival of patients with mycosis fungoides?