Vitiligo is a hypopigmentary dermatosis of probable autoimmune origin. Previously reported aberrations in peripheral blood mononuclear cells (PBMC), especially T cells and T cell subsets, have been inconsistent. Lymphocyte subpopulations were examined using flow cytometry and monoclonal antibodies against CD4, CD8, CD20, CD25, CD45RA, and HLA-DR in 34 patients with non-segmental vitiligo. Twelve patients had not received any previous treatment and 22 had previously received at least one course of PUVA therapy that was discontinued at least four months prior to our study. Compared to matched controls, we found significant increases in CD25 and HLA-DR in vitiligo patients (p = 0.000). An inverse correlation was observed between HLA-DR and patient status with regard to treatment (p = 0.001). These results suggest a role for T cells in the pathogenesis of vitiligo and imply that previous PUVA therapy may be reflected by an alteration in circulating DR +ve cells.